With the increase of existing buildings, the comprehensive renovation of existing buildings plays an increasingly important role in reducing global energy consumption and carbon emissions. By analyzing the passive technology, active technology and renewable energy technology of the existing carbon reduction renovation, the application forms of the three types of technology strategies were summarized, and their differences in carbon reduction benefits in different types of renovation such as office buildings, teaching buildings and residential buildings were compared and analyzed. On this basis, the problems existing in the current low-carbon renovation technology strategies are put forward, which will provide theoretical reference for carbon reduction renovation of existing buildings and related research.