Abstract: In order to improve the indoor thermal environment in Huizhou traditional dwellings, a patio and building envelope retrofit scheme is proposed, and the indoor thermal environment in winter is simulated by TRNSYS. It is found that the indoor thermal environment is slightly improved if only the insulating performance of building envelope is strengthened. However, indoor temperature can be increased by 3.0-4.0℃ compared to that of the original building. In addition, the probability of indoor temperature at comfortable zone is achieved over 33%, therefore, the improvement of indoor thermal environment is obviously based on the proposed building envelope retrofit scheme.