In order to improve the whole performance of search service system effectively, it proposes a method of caching mechanism optimization based on inverted file index in this paper. The specific studying process is as follows. Firstly, the system structure and data loading of inverted file caching are analyzed, and then discuss the impact of loading data to inverted file caching and cache replacement algorithm; finally, the cache optimization of inverted file is studied through designing simulation experiment. The result shows that the method of caching mechanism optimization based on inverted file index can reduce disk system I/O access times significantly, and also improve the bandwidth utilization of disk system.