Several applications in WSNs require location information of the node. These applications include location-based routing, tracking systems, dynamic networks, and health monitoring systems. There are many researchers who pay attention to localization in WSNs without more GPSs. However, minimizing error and energy consumption are the main challenge in the most of literatures. This paper is going to present an approach to localize the coordinates of nodes in WSNs. It uses graph and RSSI to estimate the distances between each sensor node and its neighbors in the target field. Then the sink collects this information to build the graph and estimate the locations. The experimental results demonstrate that the method increases location accuracy and decreases location error. Comparison with the related literatures shows that the proposed approach achieves a good result in terms of accuracy. The average error is ranging between 0.73 and 1.23 m.