To probe the catalytic effect of metal oxides in biomass on char gasification, a thermogravimetric analyzer (TGA) was used to systematically compare the gasification characteristics of deashed char (ALC) and the char loaded metal oxides (ALC-K2O, ALC-Na2O, ALC-CaO, ALC-Fe2O3, ALC-MgO). To improve result accuracy, both of the isothermal and non-isothermal gasification experiments were conducted. And the distributed activation energy model (DAEM) and Flynn-Wall-Ozawa (FWO) method were used to calculate the reaction kinetics. The results showed that the catalytic effects of metal oxides on char gasification were significantly different. Under the isothermal conditions, the gasification activity followed the order of ALC-K2O>ALC-Na2O>ALC-CaO>ALC-Fe2O3>ALC-MgO>ALC. Under the non-isothermal conditions, for the same heating rate, the characteristic reaction temperature of each char gasification (initial temperature, temperature at the maximum rate, finishing temperature) ranged the order of ALC-K2O<ALC-Na2O<ALC-CaO<ALC-Fe2O3<ALC-MgO<ALC. Lower reaction temperature indicated higher reaction activity. Kinetic analysis found that regardless of isothermal and non-isothermal operation, the calculated activation energy followed the order of ALC-K2O<ALC-Na2O<ALC-CaO<ALC-Fe2O3<ALC-MgO<ALC. This was consistent with the tested gasification behavior. Compared to the isothermal gasification, the activation energy from the non-isothermal gasification was a little large, but more stable for the different conversion rates.