For chars obtained from two different grades of coal, the variation behavior of the pore structure during the gasification process with CO2 and/or air was investigated in terms of gas adsorption methods. The increase in N-2 surface area was significant for the lower-reactive chars. Attempts were made to analyze pore size distribution in terms of N-2 ad-desorption. Air gasification (combustion) enlarged the pore size during reaction more remarkably than CO2 gasification. The softening coal char did not show the enlargement of pores as notably as the non-softening one. Correlation between variation of pore surface area and reaction rate during the gasification process was examined. The micropore surface area was proportional to CO2 gasification rate for the non-softening coal, and to air gasification rate for the softening one. There was also a correlation between only mesopore surface area and air gasification rate for some chars.