In oxyfuel combustion with temperature higher than ash flowing temperature (FT), both chemical interactions between the char gasification reaction with carbon dioxide, that is, C+CO2 --> 2CO, and the char oxidation reaction with oxygen, that is, C + (2-f)/2O(2) --> fCO + (1-f)CO2, are needed for further investigation. Both experiments and a novel developed kinetics model compared with three previous kinetics models are implemented to investigate oxy- and air-char combustion behaviors. Results show that in high temperature the maximum burning rate ratio as 34.8% from gasification is smaller than that as 47.1% in moderate temperature for inner pore reduction induced by ash mineral melting. The char mean consumption rate of sole gasification with carbon dioxide in 1773 K is 1.25 times to that in 1273 K, but this burning rate under 27%O-2/CO2 is 0.69 times to that in 1273 K. The mean burning rate ratio of char gasification increases from 28.0% to 40.0% in 1273 K and 1773 K, respectively.