diff --git a/include/graph.h b/include/graph.h
index cc06a2a..bdbb89d 100644
--- a/include/graph.h
+++ b/include/graph.h
@@ -77,7 +77,7 @@ struct _graph
     bool (*full)(struct _graph* self);
 
     // iter
-    iterator_t (*iter)(struct _graph* self);
+    iterator_t (*iter)(struct _graph* self, void *obj);
 
     // config 
     compare_fun_t compare;  // !!! you have to implement this function
diff --git a/src/graph.c b/src/graph.c
index f526ace..d421d59 100644
--- a/src/graph.c
+++ b/src/graph.c
@@ -772,6 +772,56 @@ static bool graph_find_edge(struct _graph* self, void* from, void* to)
     return true;
 }
 
+
+iterator_t graph_iter(struct _graph* self, void* start_obj)
+{
+    assert(self != NULL);
+    iterator_t iter = &self->_iter;
+
+    iter->_parent = self;
+    iter->_cur = 0;
+    iter->_cur_node = self->_head;
+
+    struct _graph_node* start = find_node(self, start_obj);
+    if(start != NULL)
+    {
+        iter->_cur_node = start;
+    }
+    return iter;
+}
+
+bool graph_iter_hasnext(struct _iterator* iter)
+{
+    assert(iter != NULL);
+    assert(iter->parent != NULL);
+
+    graph_t self = (graph_t)iter->_parent;
+    if(iter->_cur < self->size(self))
+    {
+        return true;
+    }
+    return false;
+}
+
+const void* graph_iter_next(struct _iterator* iter)
+{
+    assert(iter != NULL);
+    assert(iter->parent != NULL);
+
+    graph_t self = (graph_t)iter->_parent;
+    void *obj = NULL;
+    
+    // base on linklist
+    struct _graph_node * node = (struct _graph_node *)iter->_cur_node;
+    if(node != NULL)
+    {
+        obj = node->obj;
+        iter->_cur_node = node->next;
+    }
+    self->_iter._cur += 1;
+    return obj;
+}
+
 static bool graph_init(struct _graph* self, uint32_t obj_size)
 {
     assert(self != NULL);
@@ -799,6 +849,9 @@ static bool graph_init(struct _graph* self, uint32_t obj_size)
     self->_type = GRAPH_UNDIRECTED;
     // self->_type = GRAPH_DIRECTED;
 
+    self->_iter.hasnext = graph_iter_hasnext;
+    self->_iter.next = graph_iter_next;
+
     self->_destory = graph_destory;
 
     // -------------------- public -------------------- 
@@ -818,6 +871,10 @@ static bool graph_init(struct _graph* self, uint32_t obj_size)
     self->empty = graph_empty;
     self->capacity = graph_capacity;
 
+    // iter
+    self->iter = graph_iter;
+
+    // others
     self->from_matrix = NULL;
     self->bfs = NULL;
     self->dfs = NULL;
diff --git a/test/test_graph.c b/test/test_graph.c
index ce61549..f5fdd28 100644
--- a/test/test_graph.c
+++ b/test/test_graph.c
@@ -90,7 +90,7 @@ void test_graph_add_edge(void)
     {
         TEST_ASSERT_TRUE(graph->add_vertex(graph, &data[i]));
     }
-    graph->print(graph);
+    //graph->print(graph);
 
     // test add_edge
     TEST_ASSERT_TRUE(graph->add_edge(graph, &data[0], &data[1], 12));
@@ -98,7 +98,7 @@ void test_graph_add_edge(void)
     TEST_ASSERT_TRUE(graph->add_edge(graph, &data[1], &data[3], 24));
     TEST_ASSERT_TRUE(graph->add_edge(graph, &data[5], &data[6], 67));
     TEST_ASSERT_FALSE(graph->add_edge(graph, &temp, &data[1], 0));
-    graph->print(graph);
+    //graph->print(graph);
 
     // test find_edge
     TEST_ASSERT_TRUE(graph->find_edge(graph, &data[0], &data[1]));
@@ -109,16 +109,63 @@ void test_graph_add_edge(void)
 
     // test del_edge
     TEST_ASSERT_TRUE(graph->del_edge(graph, &data[0], &data[1]));
-    graph->print(graph);
+    //graph->print(graph);
 
     TEST_ASSERT_FALSE(graph->find_edge(graph, &data[0], &data[1]));
     TEST_ASSERT_TRUE(graph->del_edge(graph, &data[5], &data[6]));
-    graph->print(graph);
+    //graph->print(graph);
 
     graph_free(&graph);
     TEST_ASSERT_NULL(graph);
 }
 
+void test_graph_iter(void)
+{
+    const int size = 10;
+    int data[10] = {
+        0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
+    };
+    int temp = 11;
+    uint32_t i = 0;
+
+    graph_t graph = graph_new(sizeof(int));
+    TEST_ASSERT_NOT_NULL(graph);
+    graph->compare = compare_num;
+    graph->print_obj = print_num;
+
+    // test add_vertex
+    for(i = 0; i < size; i++)
+    {
+        TEST_ASSERT_TRUE(graph->add_vertex(graph, &data[i]));
+    }
+    // graph->print(graph);
+
+    // test add_edge
+    TEST_ASSERT_TRUE(graph->add_edge(graph, &data[0], &data[1], 12));
+    TEST_ASSERT_TRUE(graph->add_edge(graph, &data[0], &data[2], 13));
+    TEST_ASSERT_TRUE(graph->add_edge(graph, &data[1], &data[3], 24));
+    TEST_ASSERT_TRUE(graph->add_edge(graph, &data[5], &data[6], 67));
+    TEST_ASSERT_FALSE(graph->add_edge(graph, &temp, &data[1], 0));
+    graph->print(graph);
+
+    printf("test iter_vertex: \n");
+    iterator_t iter_vertex = graph->iter(graph, &data[0]);
+    TEST_ASSERT_NOT_NULL(iter_vertex);
+
+    printf("start\n");
+    while(iter_vertex->hasnext(iter_vertex))
+    {
+        printf("next : ");
+        temp = *(int *)iter_vertex->next(iter_vertex);
+        printf("%d\n", temp);
+    }
+    printf("end\n");
+
+    graph_free(&graph);
+    TEST_ASSERT_NULL(graph);
+}
+
+
 #if 0
 void test_graph_print(void)
 {
@@ -167,6 +214,7 @@ void test_graph(void)
     RUN_TEST(test_graph_new);
     RUN_TEST(test_graph_add_vertex);
     RUN_TEST(test_graph_add_edge);
+    RUN_TEST(test_graph_iter);
 
     // RUN_TEST(test_graph_print);
     // RUN_TEST(test_graph_from_matrix);