Abstract: The steam gasification of XLT, FG and JC coal chars was studied by isothermal thermogravimetric analysis. The relationship between reaction rate and carbon conversion of three coal chars was simulated by shrinking core model(SCM), traditional model(TM) and random pore model(RPM). The results show that TM is the best one overall for three coals. SCM and RPM are not suitable to describe the gasification process of low-rank XLT coal char, though they have satisfied simulation results to the other two coal chars with higher coal rank. The kinetic parameters were calculated by three models, and the reason for their differences was analyzed. Based on the sensitivity analysis method, the error of the prediction with the change of parameters was studied. It is shown that the apparent reaction rate k is a sensitive parameter, and the reaction order n in the TM and the structural parameter ψ in the RPM are less sensitive parameters.