Abstract-Wireless sensor network (WSN) has been paid more and more attention to by the international academic and industrial fields. What's more, it has become a hot research topic with great attention and expectations. There are a lot of technical problems involved in wireless sensor networks, among which, time synchronization technology is one of the supporting technologies in wireless sensor networks. And it is rather essential for the application of wireless sensor network. Two classical time synchronization algorithms are introduced and their advantages and disadvantages are compared. Based on the existing algorithms, an improved time synchronization algorithm is put forward. The improved algorithm was simulated by NS2. The results showed that the proposed algorithm had better time synchronization accuracy and lower network cost than RBS and TPSN algorithm. In summary, the improved time synchronization algorithm has a rather good performance.