Energy Efficiency Retrofit (EER) of existing buildings is a key program for improving building energy efficiency in northern regions of China. This paper presents a methodological framework to conduct an economic cost-benefit analysis for EER projects, based on the calculation of costs and benefits over life cycle. By conducting a case study of a retrofit project located in Huixin Western Street Residential Area, Beijing, China, this research empirically examines its economic sustainability. The research found that in China, retrofit of existing buildings generally lack of attractiveness to investors from an economic perspective. The retrofit of heat source and outdoor heating pipe networks is cost effective, whilst buildings envelopes retrofit is not economically beneficial. For building envelopes retrofit, if replacing windows using appropriate material, retrofit of external windows represents higher cost effectiveness than that of external walls. By applying sensitivity analysis, the research further discussed the effects of relevant factors on the economic viability of retrofit projects, and found that energy price is the most sensitive factor, followed by initial costs and energy conservation rate. The selection of retrofit materials also greatly influences the economic outcomes. This research offers directions for policy makers and managers to develop incentive mechanisms and management interventions to promote the implementation of the retrofit program.