Abstract: Based on the characteristics of DV-Hop,an improved scheme for this typical range-free localization algorithm in wireless sensor network is proposed.The main principle of the improved scheme is to introduce concept of collinearity degree into the selection phase of beacon nodes.Furthermore,a method for determining threshold value of adaptive collinearity degree based on the localized network topology is proposed.Not only the topology relation of beacon nodes but also the relation between unknown nodes and beacon nodes are considered in the improved algorithm.Simulation result demonstrates that the improved algorithm is more reliable and robust to irregular network topology than the traditional DV-Hop localization algorithms,especially when the ratio of beacon nodes is relatively low and the network topology is sparse.