The force of fluid particles in the filling process of horizontal centrifugal casting was analyzed, and the precipitation separation time of different kinds of inclusions and optimal pouring temperature were deduced according to the movement law of inclusions. The movement trajectory of inclusions in the filling process of horizontal centrifugal casting was established using ProCAST software, and the numerical simulation and process optimization of the movement trajectory and final residence position of inclusions in centrifugal casting pipes under different rotating speeds were carried out. Under the condition of these process parameters, the actual casting experiment of centrifugal cast pipe was carried out, and the inclusion distribution information was obtained by optical microscope (OM) and scanning electron microscope (SEM-EDS). The microscopic analysis results of inclusions in actual castings were consistent with the data simulation, which verified the effectiveness of the prediction and simulation results. The results showed that the smaller the specific gravity of inclusions and the larger the particle size, the shorter the separation time. It was found that 5 μm SiO2 inclusions were most likely to be thrown out of the liquid metal under the action of centrifugal force and finally stay on the inner surface of the cast pipe. The optimal pouring temperature for L605 centrifugal cast pipe was 1580 ℃, and the optimal centrifugal speed was 2800r/min.