Co-gasification reactivity of rice straw and bituminous coal/anthracite blended chars under CO₂ atmosphere was evaluated using thermogravimetric analysis, and the influences of coal type and gasification temperature on synergy behaviour variations on co-gasification reactivity as carbon conversions increased were quantitatively studied. Furthermore, the chemical forms and concentrations of AAEM species at different co-gasification conversions were quantitatively analyzed for revealing co-gasification synergy mechanism. The results demonstrate that as conversions increased, synergy behaviour on co-gasification reactivity of rice straw-bituminous coal blends was shown as the weakened inhibition effect firstly and then the enhanced synergistic effect. Moreover, the inhibition effect on co-gasification reactivity of rice straw-bituminous coal blends was sustained up to higher conversion with the increment of gasification temperature. Differing from rice straw-bituminous coal blends, synergistic effect on co-gasification reactivity of rice straw-anthracite blends was obviously enhanced at early stage of co-gasification and started to slowly weaken after reaching the most significant synergistic effect at middle stage of co-gasification. Additionally, it was revealed that synergy behaviour variations on co-gasification reactivity of rice straw-bituminous coal blends were mainly attributed to the combination effects of active K and Ca transformation during co-gasification, while those of rice straw-anthracite blends indicated a good correlation with active K transformation during co-gasification.