Thermal comfort and air-conditioning energy consumption are two important issues in office buildings. This paper mainly analyze the relationship between air-conditioning energy consumption and thermal comfort in different cities. Firstly, we introduce the definition of indoor cooling load, and calculate the typical office’s indoor cooling load in thirteen cities; Secondly, based on a simple equation for Predicted Mean Vote (PMV), a personalized power optimization method for air-conditioning control systems has been proposed in the paper; At last, we simulate the air-conditioning energy consumption under different thermal comfort range. The results show that air-conditioning energy saving efficiency is closely related with the acceptable comfort range and city’s geographic location. Another contribution of this study is an optimal range of thermal comfort has been presented, and this research indicates the reasonable range of PMV is about 0.5~0.7 for most of cities in China.