The interferometric range which the radio interferometric positioning system obtains is a linear combination of
distances among four sensor nodes. For the problem that the traditional localization methods using range estimstes between
a pair of nodes as input can not be applied directly in localization, a localization method based on modified particle swarm
optimization(PSO) is proposed. Experimental data of the interferometric range are used to compare the performance of two
localization methods based on genetic algorithm(GA) and modified PSO for wireless sensor networks. The results show that
the localization method based on modified PSO takes less time and achieves higher optimizing efficiency.