diff --git a/src/graph.c b/src/graph.c
index 060d440..64bc5df 100644
--- a/src/graph.c
+++ b/src/graph.c
@@ -851,7 +851,7 @@ const void *graph_iter_next(struct _iterator *iter)
         struct _graph_node *cur_node = iter->_cur_node;
         struct _graph_edge *cur_edge = cur_node->edgehead;
         struct _graph_node *target = NULL;
-        struct _graph_node* node = cur_node;
+        struct _graph_node *node = cur_node;
 
         queue_t queue = self->queue;
 
@@ -860,7 +860,7 @@ const void *graph_iter_next(struct _iterator *iter)
             cur_node = self->_head->next;
             while (cur_node != NULL)
             {
-                if(cur_node->visited != true)
+                if (cur_node->visited != true)
                 {
                     queue->push(queue, &cur_node);
                     break;
@@ -878,10 +878,10 @@ const void *graph_iter_next(struct _iterator *iter)
             while (cur_edge != NULL)
             {
                 target = cur_edge->target;
-                if(target != NULL && target->visited != true)
+                if (target != NULL && target->visited != true)
                 {
                     queue->push(queue, &target);
-                                            
+
                     // self->print_obj(node->obj);
                     // printf(" -> ");
                     // self->print_obj(target->obj);
@@ -899,43 +899,75 @@ const void *graph_iter_next(struct _iterator *iter)
     case GRAPH_DFS:
     {
         // self->stack->push(self->stack, iter->_cur_node);
-        struct _graph_node* cur_node = self->_iter._cur_node;
-        struct _graph_node* node = NULL;
+        struct _graph_node *cur_node = self->_iter._cur_node;
+        struct _graph_node *node = NULL;
         struct _graph_edge *cur_edge = cur_node->edgehead;
         struct _graph_node *target = NULL;
 
         stack_t stack = self->stack;
- 
-        while (!self->stack->empty(self->stack) || cur_node != NULL)
+
+        // while (!self->stack->empty(self->stack) || cur_node != NULL)
+        do
         {
-            if (cur_edge != NULL)
+            if(cur_node == NULL)
+            {
+                break;
+            }
+
+            if(cur_node->visited == true)
+            {
+                stack->pop(stack, &cur_node);
+                cur_node->visited = true;
+                node = cur_node;
+                break;
+            }
+
+            bool accessible_vertex_exists = false;
+
+            // 1. add cur_node to stack
+            stack->push(stack, &cur_node);
+
+            // 2. find the first unvisited vertex
+            cur_edge = cur_node->edgehead;
+            while(cur_edge != NULL)
             {
                 target = cur_edge->target;
                 if(target != NULL && target->visited != true)
                 {
-                    stack->push(stack, &target);
+                    accessible_vertex_exists = true;
+
+                    cur_node = target;
+                    break;
                 }
                 cur_edge = cur_edge->next;
             }
-            else
+            
+            iterator_t iter = stack->iter(stack);
+            struct _graph_node *temp_node = NULL;
+            while (iter->hasnext(iter))
             {
-                iterator_t iter = stack->iter(stack);
-                while(iter->hasnext(iter))
-                {
-                    struct _graph_node* g_node = *(struct _graph_node **)iter->next(iter);
-                    self->print_obj(g_node->obj);
-                }
-                printf("\n");
+                temp_node = *(struct _graph_node **)iter->next(iter);
+                self->print_obj(temp_node->obj);
+            }
+            printf("\n");
 
-                self->stack->pop(self->stack, &cur_node);
-                node = cur_node;
-                cur_node = cur_node->next;
+            if(accessible_vertex_exists != true ||
+                cur_edge == NULL)
+            {
+                // if no accessible vertex, pop from stack
+                stack->pop(stack, &node);
+                node->visited = true;
+
+                stack->peek(stack, &cur_node);
                 break;
             }
-        }
-        
-        iter->_cur_node = node;
-        obj = cur_node->obj;
+        }while(!stack->empty(stack));
+
+        printf("--- end ---\n");
+        iter->_cur_node = cur_node;
+        printf("--- end1 ---\n");
+        obj = node->obj;
+        printf("--- end2 ---\n");
     }
     break;
     default:
diff --git a/test/test_graph.c b/test/test_graph.c
index 5f95869..7ace9b6 100644
--- a/test/test_graph.c
+++ b/test/test_graph.c
@@ -166,7 +166,7 @@ void test_graph_iter(void)
     while(iter_vertex->hasnext(iter_vertex))
     {
         temp = *(int *)iter_vertex->next(iter_vertex);
-        // graph->print_obj(&temp);
+        printf("temp = %d\n", temp);
     }
 
     graph_free(&graph);