Usingfiber reinforced plastic (FRP) pipe in the coalbed methane horizontal well can enhance the security of later coal mining. For revealing centralitychange rules of FRP pipe at different stages of cement slurry displacement at different time during coalbed methane horizontal well cementing, on the basis of analysis on buoyant weight of FRP pipe, a centrality calculation model is established by considering the influence of centralizers. The result of the research shows that, because of the low density of the FRP pipe, it will float upward instead of sinking when fluid density changes inside and outside of casing, and its location and centrality may dynamically change. So a lower density of slurry is in favor of reducing buoyant weight of FRP pipe and enhancing its centrality. This research providestheoreticalbasis for the improvement of centralizer for the FRP pipe.