In order to carry out an ex-post assessment of the completed Building Energy Efficiency Special Planning, a comprehensive ex-post assessment methodology is established. The methodology sets out the ex-post assessment criteria from three dimensions and 27 indexes, and apply the Fuzzy Synthetic Evaluation Method to build the ex-post assessment model. Applying the methodology, this research assesses the effectiveness of the Building Energy Efficiency Special Planning in Beijing during the “12th Five-Year Plan” period. The results show that it is generally effective in terms of realizing the main planning targets, reaching the desired development level of Building Energy Efficiency and ensuring the facilitating mechanisms to be in place. To be specific, substantial increase of the proportion of energy efficient buildings and considerable effects of energy saving and carbon emission reduction have been achieved, whilst the electricity consumption per unit area in small and median-sized commercial buildings being increased. The research further identifies the main barriers to the implementation of building energy efficiency program includes high electricity consumption of large-scale commercial buildings, insufficient data information, slow uptake of modern information technology, lack of market participation and lack of wider social recognition. Based on the assessment result and subsequent analysis, commensurate policy recommendations were proposed. This research was the first attempt examining the implementation effects of BEE Special Planning in Beijing.