In China, more than 30% of energy consumption is due to the building sector, in which office buildings play an important part due to their structural characteristics and high quality build requirement. The whole life-cycle of an office building presents a great environmental impact, which is normally difficult to define and statistise. This paper introduces a calculation method for pollutant emissions for the whole life-cycle of office buildings in China, in which the non-comparable discharge amount of each pollutant is converted to comparable monetization of environment cost. According to the description of the calculation method and a case study, the phase distribution of pollutant emissions and the environmental cost of an office building will be summarized, the relationship between “green-design” factors and life-cycle environmental costs will be discussed through the analysis of feasible design modification. According to this study, the characteristics of life-cycle environmental costs of office buildings and the significant of “green design” will be analysed providing important information for future office building design and green renovation in China.