This study investigates the carbon reduction practices and evaluates the operational effectiveness of an existing green office building located in the Hot Summer and Cold Winter (HSCW) Zone of China. Focusing on the Chongqing Design Institute Building Research Building, the research integrates both objective testing and subjective occupant surveys to assess the building's energy consumption and indoor environmental quality. A series of operational optimization strategies were implemented, including energy-efficient systems and behavior-oriented guidelines for occupants, aimed at reducing carbon emissions and improving satisfaction with the indoor environment. The study employs quantitative methods to evaluate the building's carbon emissions and occupant satisfaction before and after the strategy implementation. The results show a significant reduction in carbon emissions per unit building area and a notable increase in occupant satisfaction, with operational effectiveness improving from a B-level in 2022 to an A-level in 2023. This case study demonstrates that targeted operational strategies can effectively achieve carbon reduction goals while maintaining high levels of occupant satisfaction in green office buildings in China's HSCW climate zone.