Abstract: On the basis of experimental study on exhaust emissions in a single tube combustor and a vaporiser tube combustor, a theoretical analysis and mathematical modelling are made by using heterogeneous Well Stirred Reactor Analysis (WSR). Considering rea! combustion processes and different combustion structures, the General Reactor Analysis and Simulation Program (GRASP) are improved and supplemented. A new method is put forward to process the distribution of mixture mass with different φand to determine exit flow parameters in the primary zone. This paper aiso deals with the secondary air flow and its mixture with primary gases, the local fuel-rich treatment and the calculation of equilibrium temperature and compositions, in this way, the GRASP has been developed from one only for a simple model combustor to a modification able to predict 17 emission compositions and combustor exit temperature for two real gas turbine comb tors. The results predicted by the modified GRASP are in good agreement with measured data. The prediction also confirms the conclusion drawn from experiments that the emission pollution performance of the vaporiser tube combustor is better than that of the single tube combustor. Moreover, it is found that the errors in prediction of the exit temperature are one of the reasons which cause the errors in NO_X prediction.