Abstract: This study utilizes Swire simulation technology to conduct a building performance evaluation and green retrofit optimization for the library building at the Deyang Campus of Sichuan Nursing Vocational College. Addressing identified issues in the existing structure， including inadequate daylighting， excessive noise levels， high energy consumption， and significant carbon emissions， a systematic retrofit strategy was developed. Key interventions encompassed： significantly improving daylight factor compliance through the installation of a light-guiding system， replacement with high-performance glazing， and optimization of interior surface reflectance ratios； effectively controlling indoor noise levels via sound barriers， upgraded external window assemblies， and strategic placement of acoustic absorptive materials； enhancing the thermal performance of the building envelope by applying thermal insulation layers to external walls and the roof； and reducing operational energy consumption through the integration of solar photovoltaic systems， rainwater harvesting， and natural ventilation strategies. Post-retrofit， the building demonstrated marked improvements in daylighting， acoustic insulation， thermal performance， and energy efficiency. A substantial reduction in lifecycle carbon emissions was also achieved. This project provides a reference for optimizing the green performance of similar public campus buildings.