A perfect range-free node localization algorithm for WSNs is proposed.Weight is introduced into the algorithm to improve the calculation method of average hop-distance.Virtual anchors is introduced into the algorithm to increase the coverage rate of network

and location is estimated by selecting suitable anchor node group and introducing collinearity threshold NCD and a hop threshold THD.The final position coordinates can be obtained by using Centroid algorithm.Simulation results show that the novel DV-Hop algorithm can provide more accurate location estimation and has good coverage character.It does not need any additional hardware device.