A model for coal gasifiers was proposed from the combination of the Kunii-Levenspiel bubbling bed model and our own grid zone model. Based on the model, local contribution of individual reaction was analyzed and local concentration profile was predicted in the grid and bubbling zones of a laboratory scale fluidized coal gasifier. The effects of lateral temperature and bed height on CO, H-2 and CO2 concentration were discussed by comparison with experimental results. The results showed that the numerical predictions are corresponding to the experimental ones. It has been verified that combustion occurs mainly nearby the jet region, steam gasification both in the annulus and emulsion regions and CO2 gasification mainly in the emulsion region. It is clearly shown that the contribution of the progress of the reactions in the grid zone to total gasification performance is high.