Abstract: Agricultural and forestry residues, as vital biomass resources, are recognized for their potential in high-value energy conversion, providing an effective pathway toward sustainable development and dual-carbon goals. A cascade conversion model integrating photo-fermentative biohydrogen production with microwave pyrolysis is developed to overcome the limitations of single conversion technologies. By coupling biological and thermochemical processes, efficient stepwise utilization of all biomass components is achieved. Five representative lignocellulosic residues (wheat straw, rose stem, bamboo, cotton stalk, and peanut stem) are employed as feedstocks to investigate the cascade hydrogen production process under conditions of 20 g feedstock, 20 min pyrolysis time, and 800 W microwave power. Gas chromatography (GC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and nitrogen adsorption (BET) surface area analysis are applied to elucidate the mechanisms of material transformation, residue composition evolution, and product distribution during hydrogen production. Results indicate that, under light-driven anaerobic conditions, carbohydrates are degraded and dehydrogenated by the photosynthetic bacterial consortium through nitrogenase- and hydrogenase-mediated pathways, yielding 7.994 to 21.211 mL/g of hydrogen. The post-photo-fermentation residues are primarily enriched in recalcitrant lignin, along with residual cellulose and hemicellulose. Subsequent microwave pyrolysis further converts the remaining organic matter into hydrogen (87.970 to 226.905 mL/g) via thermal cracking, decarboxylation, and aromatization reactions. Bamboo shows the highest total hydrogen yield (242.235 mL/g), corresponding to a 422.35% increase compared with single-stage photo-fermentation. In addition, microwave pyrolysis demonstrates strong potential for carbon resource valorization, exemplified by a biochar yield of 54.640% from rose stem residue, and for methane production, with bamboo residue generating 44.812 mL/g.