Abstract: Affected by climatic conditions and functional characteristics, primary and secondary school buildings in hot-summer and warm-winter regions generally face the problem of high energy consumption. Taking a nine-year school in Tianhe District, Guangzhou as the research object, this paper conducts an optimization study on energy-saving design, aiming to improve building energy efficiency, implement local energy-saving policies, and provide a reference for campus design in the same climatic zone. The study adopts the strategy of "passive energy conservation first, supplemented by active technologies". It enhances thermal performance by guiding natural ventilation through a "stacked garden" layout, controlling solar radiation via differentiated sun shading, and implementing three-dimensional thermal insulation for "external windows, walls and roofs". A comprehensive energy-saving scheme is further established by integrating intelligent equipment, lighting control systems and solar photovoltaic systems. The results show that the thermal performance of the project exceeds current codes; the maximum indoor temperature of classrooms in summer is reduced by 3 °C to 5 °C, and the air-conditioning load is significantly decreased. The annual air-conditioning energy consumption is 35 kWh/(m²·a), 40% lower than that of non-energy-saving buildings. The carbon emission intensity is 41.59% lower than the 2016 standard, with an annual carbon emission reduction of 14.21 kgCO₂/m². All indicators meet energy-saving and energy-efficiency requirements. This study demonstrates that the design principles of "heat transfer control, radiation prevention and heat dissipation" are compatible with the climatic characteristics of hot-summer and warm-winter regions, and the technical path of "passive measures as the mainstay, active measures as supplements" is feasible and effective. It can serve as an engineering example and reference for the energy-saving design of primary and secondary school buildings in similar climatic zones.