Information Security Education Journal Qingjian Ni, Cen Cao 3 2 2016 Node localization is an essential problem for some engineering applications in wireless sensor network (WSN). In this paper, an improved node localization method is proposed by combining the particle swarm optimization (PSO) and evaluation of environment variables. Firstly, the problem characteristics of node localization in WSN are analysed, and then a framework and a strategy for the settings of important parameters are given to solve such problems with PSO. Furthermore, the environment variable of WSN is evaluated and an improved node localization method based on PSO is proposed. In the proposed node localization method, the environment variable of WSN is evaluated during the process of ranging and the fitness function of PSO is designed according to the environment variable, and then the PSO algorithm is adopted to solve the node localization problem. Compared with the traditional methods, the results of simulation experiments show that the proposed method has good performance on the core indicators. Besides, for the proposed model and method, we also discussed the impact of several factors on the localization performance, which include the number of nodes, the number of failure nodes, the positioning error and the mean distance-measuring error.