In the present study the catalytic steam gasification of biomass to produce hydrogen-rich gas with calcined dolomite and Nano-NiO/gamma-Al2O3 as catalyst in an externally heated fixed-bed reactor was investigated. The influence of the catalyst and reactor temperature on gasification performance was studied at the temperature range of 700-900 degrees C. Over the ranges of experimental conditions examined, Nano-NiO/gamma-Al2O3 and calcined dolomite both revealed better catalytic performance, at the presence of steam tar was completely decomposed as temperature increases from 800 to 900 degrees C. A higher temperature resulted in more H-2 and CO2 production, and dry gas yield. The highest H-2 content of 51.02 V% and the highest H-2 yield of 1.66 m(3)/kg biomass were observed at the highest temperature level of 900 degrees C.