With calcium carbonate and barium carbonate as desulfurizers, combustion desulphurization experiments of coal water slurry and pulverized coal were respectively done in the ZCL. The results show that desulfurization efficiency in coal water slurry is prior to the same pulverized coal. The desulfurization characteristic of desulphurizing coal water slurry was analyzed by comparing the desulfurization efficiency of coal water slurry and pulverized coal. The reaction atmosphere in the boiler is different from the pulverized coal because of water evaporation ,and the CO content was lower ,so the decomposing rate for desulphurization products was reduced,after water evaporated ,it formed microstructures which was considered as favorable to the desulfurization rate .