Thermochemical conversion of agricultural by-products into hydrogen-rich syngas is a technology that offers both economic and environmental benefits. In this work, we investigated a biochar-supported nickel-based catalyst for the catalytic pyrolysis of straw biomass to produce hydrogen-rich syngas. The by-product, straw biochar, was used as a material for synthesizing fresh catalysts, achieving a closed-loop process. We explored gas yields under various conditions. The highest yields of CO and H2, reaching 0.52 L/g and 0.48 L/g, respectively, were obtained under the conditions of a pyrolysis temperature of 900 °C, a residence time of 20 min, a calcination temperature of 400 °C, a nickel loading of 15 wt%, and a citric acid to potassium hydroxide ratio of 1:4. The catalysts were characterized using XRD, H2-TPR, SEM, and TEM. The results demonstrated that biochar provides excellent support and synergy, enabling the catalyst to function at high temperatures and offering antioxidative protection to the active metals during the thermal process. Overall, this catalytic pyrolysis process, aiming for green and efficient conversion, achieved high yields of syngas and hydrogen. •Biochar provides anti-oxidation protection for active metals.•Biochar-supported Ni catalyst shows high load capacity and synergy.•Utilizing biochar byproduct to synthesize fresh catalyst, enhancing syngas yield.