Based on the steam gasification experiments of “Fujian Jianxin” anthracite with different catalyst loadings of Na2CO3 in the thermal balance at 850℃，decomposition of Na2CO3 itself and mass loss arising from the reaction of Na2CO3 with carbon in coal were examined.Also，the change of adsorption-desorption isotherms of coal samples at different conversions were measured with the specific surface area analyzer.Type Ⅰ adsorption-desorption of a narrow slit micropore configuration with a close end was mainly shown at a lower Na2CO3 loading and lower conversions，while type Ⅱ adsorption-desorption of open mesopores and macropores with two-end opening holes was formed at a higher Na2CO3 loading and higher conversions.H4-type hysteresis loop with slit and ink-bottle pore surface appeared at and beyond 〖JP2〗the catalyst saturation loading of 12% Na2CO3.The specific surface area and pore-size distribution at different Na2CO3 loadings and conversions were calculated using BET equation and T-plot model.These calculation indicated that all of specific surface area appeared to be increasing at first then decreasing with increasing conversion extent of coal.The split and crosslinking of more micropores and the reduction of micropore specific surface area were the result of the increase of active sites of carbon and gasification rate due to the loading and dispersing of Na2CO3 catalyst.The change of specific surface area with increasing at first then decreasing became more smooth with more loading of Na2CO3.At the catalyst saturation loading of 12% Na2CO3，the sufficient filling and uniform dispersion of catalyst led to increase of active sites on micro-crystalline structure surface of more inert carbon and the split and crosslinking expansion of more micropores in the gasification process.However，at the termination gasification reaction with deep conversion，all of specific surface area were close to zero，clearly showing maximum conversion of coal and uniform gasification at catalyst saturation loading.