This study explores optimization strategies for hydrogen-methane co-production from enzymatically hydrolyzed corn stover, focusing on the effects of timed hydrogen effluent (HE) addition on methane yield and underlying mechanisms. Enzymatic hydrolysis produced a cumulative hydrogen yield of 53.6 ± 3.2 mL/g total solids. Optimal conditions were determined using a Box-Behnken design. These included an enzymatically hydrolyzed stover concentration of 2.8 %, an HE concentration of 398 mL/L, and HE addition on day 11, yielding a cumulative methane production of 490.8 ± 20.0 mL/g volatile solids. HE addition enhanced methane production by increasing volatile fatty acid concentrations, stimulating Proteobacteria growth, and balancing metabolic activity between Methanosarcinales and Methanomicrobiales. Furthermore, life cycle analysis showed that the hydrogen-methane co-production system reduced energy consumption by 25.0 % and carbon emissions by 7.4 % compared to the control group, highlighting its sustainability. This study provides a new perspective on the resource utilization of corn stover.