The escalating crisis of global warming, driven by the emission of greenhouse gases, poses a formidable challenge for humanity as a whole. Notably, the construction industry contributes significantly to the global greenhouse gas inventory. Consequently, prioritizing low-carbon construction assumes paramount importance in mitigating the pervasive impact of the greenhouse effect on a global scale. Such an endeavor stands as a crucial safeguard for ensuring the sustainable development of human civilization. Therefore, from the perspective of low- carbon building design optimization research is an important part of low-carbon building. From the perspective of architectural design, this paper summarizes that low-carbon building design should pay attention to following aspects: reasonable use of natural lighting and natural ventilation, reduce the carbon emission value of building use stage; Taking the transformation project of the former engineering Institute of Southeast University as an example, this paper probes into the effect of design optimization on reducing carbon emissions, and quantitatively studies the relationship between the design optimization of lighting, ventilation and envelope structure materials and the reduction of building carbon emissions. The Angle selection of roof skylight is studied from the Angle of day- lighting optimization, the size and position of facade opening and the strategy of natural ventilation path are studied from the Angle of ventilation optimization. The indoor ventilation further reduces the refrigeration energy consumption, which is 22.1% less than before the renovation, and the roof reduces the heat gain by 22%-32%.e.