The variation of the apparent reaction order, n, during char combustion is studied by simulating the combustion process inside the char particle pores. An expression for n is obtained as a function of the particle temperature, the O-2 partial pressure, and the pore structural parameters. A modulus, chi, is shown to represent the pore diffusion resistance, with a sufficient condition for n = 1 given based on chi. n becomes lower as the particle temperature and the O-2 partial pressure increase and the pore structure has higher diffusion resistance. The expression for n is used to improve the accuracy of a previous fractal char combustion model. The effect of n on the char combustion rate and the regularity of how n changes in the char combustion process are also studied.