A bubbling fluidized-bed gasification system was selected for catalytic steam gasification of rice straw with four Ni-based catalysts, i.e., Ni/Al2O3, Ni/CeO2, Ni/MnO2, and Ni/MgO. The effect of temperature, steam/biomass ratio (S/B), and catalyst/biomass ratio (C/B) on the gas composition, char conversion, and hydrogen yield was evaluated. It was found that higher temperature and S/B promote hydrogen production and char conversion. The results also demonstrated that the catalytic activity of Ni/Al2O3 under different S/B values is better than those of the other catalysts. Regarding the catalyst activity, all four catalysts exhibited good performance in terms of tar removal and carbon conversion. However, the performance of Ni/Al2O3 was superior to that of the other three catalysts.