For rotary engine, the changes in port timing can bring change, not just to admission efficiency, but to the the flow field and turbulence energy in cylinder. On the basis of the Fluent simulation software, a threedimensional dynamic simulation model was established through the secondary development to write dynamic mesh programs and choose the reasonable turbulent model, combustion model and CHEMKIN mechanism. The threedimensional dynamic simulation model based on the chemical reaction kinetics was also validated by using the experimental data. On this basis, the working process of peripherally ported natural gasfueled rotary engines under different port timings was simulated. The results show that with the intake duration angle unchanged, as the intake opening angle was brought forward, the intensity of the swirls and the vortex blobs, the volumetric coefficient all increased, and the turbulence intensity near the ignition position also increased. The increase of the turbulence intensity near the ignition position can significantly increase combustion rate, but the whole combustion rate in combustion stage did not always increase with advanced intake opening angle. With the intake duration angle unchanged, when the intake opening angle was 407°, the flame propagation speed reached the maximum value, the indicator diagram was the best and the emission of NO was the biggest.