Abstract: As an emerging secondary energy source, hydrogen boasts high energy density and inherent cleanliness with zero pollution, making it one of the most promising alternatives to fossil fuels. Against the backdrop of the growing global consensus on low-carbon development and the urgent demand for clean hydrogen production, the production of green hydrogen using renewable energy sources such as biomass represents a key direction for the development of hydrogen energy. Biomass chemical looping gasification and reforming for hydrogen production （CLHP） represents a novel technology for producing synthesis gas and hydrogen. In this study, a series of A-site （La, Sr, Cr, Mn） doped CoFe₂O₄ spinel oxygen carriers were synthesized via a sol-gel method. The performance of the obtained oxygen carriers in biomass CLHP was systematically evaluated in a fixed-bed reactor simulating a three-bed system for the final products of synthesis gas and hydrogen with walnut shells and steam as feedstocks. Characterization techniques including XRD, EPR, BET, and H₂−TPR were employed to investigate how A-site doping modulates CoFe₂O₄ performance in biomass CLHP. The results show that A-site doping can effectively improve the hydrogen production performance of oxygen carriers, and the hydrogen yield per unit mass of oxygen carriers（OCs） after A-site doping follows the order of La > Cr > Sr > Mn. Among the doped samples, La−doped CoFe₂O₄ exhibits the highest hydrogen production rate of 297 mL/g. A-site doping effectively modulates oxygen vacancy concentration and surface oxygen species distribution. La doping induces lattice distortion, increases vacancy concentration, and promotes lattice oxygen migration during hydrogen evolution by optimizing structure and thermodynamics. The hydrogen production rate rises with increasing A-site doping concentration. The doped OC also exhibits excellent stability over multiple redox cycles. This work provides fundamental insights and critical data for the rational design of high-performance spinel oxygen carriers for biomass CLHP.