Abstract: To address the high production cost caused by grain-based carbon sources in 3-hydroxypropionic acid (3-HP) biosynthesis and make full use of abundant biomass resources in China, this paper takes corn straw as raw material and constructs an integrated system for 3-HP production coupled with biomass gasification, water electrolysis for hydrogen production and biocatalytic conversion. Different from existing routes of independent 3-HP fermentation or gasification-electrolysis for methanol-only production, the proposed system realizes the serial coupling of methanol synthesis and 3-HP bioconversion for cascade carbon utilization. In the proposed system, crude syngas is obtained through pyrolysis, gasification and catalytic reforming of corn straw. The inherent hydrogen-carbon ratio of syngas fails to meet the requirement of methanol synthesis; thus, alkaline water electrolysis is adopted to adjust the gas composition. The generated methanol is further converted into 3-HP via fed-batch fermentation of methylotrophic microorganisms, and excess hydrogen produced in the process can be sold as a by-product. Aspen Plus, a thermodynamic simulation software, is applied to simulate the whole system. Thermodynamic analysis is carried out based on energy and exergy balance, and techno-economic evaluation of the system is completed combined with equipment investment, raw material cost and product revenue. The results show that the 3-HP output reaches 39.67 kg/h, the overall energy efficiency is 22.50%, the total exergy efficiency is 28.00%, and the dynamic payback period is 2.23 years. This coupled integrated process exhibits favorable thermodynamic conversion performance and promising potential for industrial application.