KOH/dolomite composite catalyst was used to catalyze steam gasification in a fixed-bed gasifier with pine sawdust as raw material. The effects of catalyst preparation conditions, reaction temperature, steam flow rate and catalyst dosage on the evaluation indexes of gasification characteristics such as gasification synthesis hydrogen content, gas yield, hydrogen yield and carbon conversion rate were investigated. SEM, XRD and pore structure analysis of the K/Ca composite catalyst were carried out. The results showed that K element was well loaded on dolomite. The K/Ca composite catalyst prepared by KOH mass fraction of 6%, K/Ca molar ratio of 2∶1 and calcination at 900 ℃ had the best catalytic performance. When the gasification temperature increased from 600 to 750 ℃, the H2 volume fraction increased from 40.70% to 59.09%, and the hydrogen yield rate increased from 16.38 to 90.64 g/kg. However, the catalyst activity decreased owing to the continuous increase of temperature, and the H2 volume fraction and hydrogen yield decreased as well. When the steam flow rate increased from 0.4 to 1.0 mL/min, the H2 volume fraction increased from 52.75% to 59.09%, and the hydrogen yield increased from 68.14 to 90.64 g/kg. Further increase of steam flow would lead to heat loss in the system, which would reduce the H2 volume fraction and hydrogen production rate. When the mass ratio of catalyst to raw material was 0.3 g/g, the volume fraction of H2 was 59.09% and the yield rate of hydrogen was 90.64 g/kg. When the mass ratio increased to 0.6 g/g, the volume fraction of H2 decreased to 58.50%, and the hydrogen production rate increased to 103.18 g/kg. When the mass ratio of biomass continuously increased, above growth became significantly slow, that was, the catalytic reaction basically reached equilibrium. With the consideration of the various aspects, the optimal conditions of K/Ca composite catalyst for pine sawdust steam gasification were as follows: reaction temperature of 750 ℃, water vapor flow rate of 1.0 mL/min, and mass ratio of catalyst to raw material of 0.6 g/g. At this time, volume fraction of H2 in product gas was 58.50%, hydrogen production rate was 103.18 g/kg, the low calorific value was 10.94 MJ/m3, and carbon conversion was 83.25%.