Abstract: It is important to study the effects of pyrolysis and ablation of heat protection material in integrated design of hypersonic vehicles. In order to predict and assess the material pyrolysis and ablation effects on target signatures and microwave communication, based on chemical nonequilibrium gas dynamic equations and solid heat transfer equations, the general surface conditions to couple flowfield with heat shield and the thermophysical and chemical models were set up. The method to solve governing equations for hypersonic flowfield and ablator heat transfer was established, and the feasibility of such model and method was validated. In addition, the flowfield and wake over reentry body with complex shape and silicon-based heat protection material were simulated numerically and the influence of the material pyrolysis and ablation on plasma distribution were analyzed. The study shows that the effects of pyrolysis and ablation on plasma distribution are small in the absence of alkali metal element in the surface materials, and the effects on plasma distribution are significant in the case of containing trace amounts of alkali elements. For the latter case, its influence on reentry target signatures and microwave communication can not be ignored.