Abstract: Abstract: Improving pyrolysis gas quality is a hot issue in biomass pyrolysis gasification technology. In recent years, it has been generally accepted that the addition of a catalyst can effectively improve the pyrolysis effect of biomass. Biochar, as a by-product of biomass pyrolysis, has the advantages of strong adsorption, low deactivation, good catalytic effect, and low cost. In this paper, biochar was used as a catalyst to investigate the steam reforming of biomass pyrolysis volatiles. And, corn stalk granules were selected as the research object. The ex-situ catalysis method was used to form a stable catalytic carbon bed above the grate so that the biomass charcoal fully acted on the pyrolysis volatiles, and the steam condition was added during the test to improve the biochar. For the catalytic effect of pyrolysis gas, Fe2O3(adding ratio of 10%) and CaO (adding ratio of 10%) were used as auxiliary agents to enhance the catalytic activity of biomass carbon and to improve the biomass pyrolysis gas. The corn straw was 5 g, the flow rate of stream was 0.5 mL/min, the reaction temperature were set on 600, 700 and 800 ℃.The test results showed that the pyrolysis gas components of the corn straw granule gasification test mainly include CH4, CnHm, CO, CO2, and H2. After adding biochar, the quality of pyrolysis gas was effectively improved, especially the gas component of H2 in pyrolysis gas was increased. The increase was most obvious at 800 ℃, which was 7.3% higher than that without biochar. The amount of pyrolysis gas was also increased, increasing up to 1 238 mL at 700 ℃. The addition of the biochar-Fe catalyst could significantly increase the gas volume of pyrolysis gas, especially the H2 in pyrolysis gas. The H2 gas in pyrolysis gas was 2 987 mL at 800 ℃, compared with none, biochar and biochar-Ca, they were increased by 1803, 1 261, and 1 055 mL at the same temperature. Biochar-Fe have a good promoting effect on the preparation of hydrogen-rich pyrolysis gas. The biochar-Ca catalyst could increase the calorific value of the pyrolysis gas, and the addition of CaO had the effect of absorbing CO2 in the pyrolysis gas. The maximum value reached 14.22 MJ/m3 at 800℃, and its calorific value increased by 2.62, 2.7 and 3.85 MJ/m3 at the same temperature than none, biochar and biochar-Fe. It is seen that CaO can be used as an auxiliary for preparing higher calorific value gases.