The average per-hop distance is one of the factors which affect the positioning accuracy in DV-Hop algorithm. Aiming at positioning errors caused by the average distance per hop, the average distance per hop of anchor nodes and unknown nodes have been improved and optimized in this paper. First, the average per hop distance of anchor nodes is computed by introducing genetic algorithm; Then the average distance per hop of the unknown node is weighted by using the average distance per hop of anchor nodes which hop count is less than or equal to 3 to reduce errors caused average distance per hop. Ultimately the accuracy of positioning is improved. Simulation results show that without additional hardware cost, the improved algorithm can effectively improve the positioning accuracy of the algorithm and has good stability.