Abstract: A detailed description of the methods used to evaluate the non-equilibrium and catalytic surface effects on thermal environment of the reentry vehicles is presented. There are lots of engineering prediction models for non-equilibrium effects since 1950s, most of them based on the hypothesis that the boundary layer is frozen and recombination of the dissociated gases only occurs at the wall surface depending on the wall catalytic properties. Five widely used methods for one same question are selected and compared, and their results are quite different from one another. Based on recently numerical results and theoretical analysis, a new model which takes chemical reactions both in boundary layer and on body surface into account simultaneously is proposed in this paper. It is shown that the chemical state of the boundary layer is controlled mainly by the recombination that takes place near the wall, which suggests representing the gas-phase reaction by an equivalent surface reaction with all state variables specified by surface conditions. The equivalent surface reaction method then can be extended to the case in which the surface has an arbitrary catalytic. The results obtained by this proposed model agree quite well with the flying test data of STS-2 space shuttle. From the calculation results, the non-equilibrium effect often appears when the vehicle flight altitude is above 50 km at atmosphere accompanied by the rarefied flow effects, and the non-equilibrium effect mainly occurs near the nosetip regions. At the place far down the nosetip, the chemical state of the boundary layer will transfer to equilibrium.