Semantic caching is very attractive for use in distributed computing environments based on historical queries and their descriptions, one of whose important issues is how to best maintain semantic caching using a coherency control scheme. With the object of applying semantic caching into practice, the cache coherency problems including the data between the server and its caching as well as the cached data and their semantic descriptions are analyzed. This paper presents conflicts existing in semantic caching and their formal definitions, proposes the semantic caching model, and coherency control scheme, meanwhile derives update list optimization algorithm adopted in server and coherency control algorithm used in clients. Finally, the performance of the semantic caching coherency control scheme is examined and analyzed through a simulation study in detail.