Abstract: Shengli brown coal in 150-180 μm was gasified at 800-900℃ in a simulated entrained-flow reactor, φ80×3 000 mm. Conversion and kinetics of steam gasification reaction of the lignite were discussed to investigate synergistic effects of oxidation reaction on steam gasification reaction. The results show that lignite conversion under H₂O+1%O₂ atmospheres is greater significantly than the sum of that under H₂O atmosphere and 1%O₂ atmosphere, i.e., the increase of lignite conversion from H₂O atmosphere to H₂O+1%O₂ atmospheres is greater than that from N₂ atmosphere to N₂+1%O₂ atmospheres. The synergistic effects are caused by promoting effect of oxidation reaction on steam gasification reaction, and are more obvious as H₂O content increasing and temperature rising. Moreover, the similar experiments were carried out in φ40×200 mm cylindrical quartz fluidized bed, and the synergistic effects are also found. The steam gasification reaction rate equation, (Z-(1-x)^\frac13)=\fract\beta k_\textH_2\textOR\rho _\textC\varphi _\textH_2\textO=K_\textH_2\textO\varphi _\textH_2\textO , is in good agreement with experimental data. This indicates that the apparent rate constant K_H2O increases obviously after O₂ adding to water vapor, which is the kinetic characteristics of promoting effect of oxidation reaction on steam gasification reaction.