Abstract: Presented by Hoekstra in 2002, grey water footprint is a method which describes the pollution status in quantitative way. Grey water footprint is defined as the fresh water volume needed to dilute the pollutant to the maximum concentration allowed by relevant water quality standards. Although this theory provides a new way to assess the condition of water environment pollution, it has several problems when taken in practical application. Firstly, the traditional grey water footprint computation does not consider the fact that the pollutant is usually diluted by different water bodies, so the result figured out only shows the total grey water footprint but fails to reflect the pollution severities of different water bodies; secondly, equating massive discharge of pollutant with large grey water footprint can lead to an incorrect computing result of grey water footprint. On account of these reasons, an improved computing method of grey water footprint is hereby presented. The improved method is a two-step ap-proach, which takes into consideration the fact that the same pollutant can be diluted by several water bodies, and attaches much importance to different demands on different pollutants by water quality standard, thus it can distinguish the two concepts of large grey water footprint and massive discharge of pollutant. The improved method firstly divides the whole quantity of discharged pollutant into several different water bodies and calculates the grey water footprint of each water body based on the “maximal counts” principle, and then sums up the grey water footprints of different water bodies to get the final grey water footprint. The concept of water environment load index is also introduced, and it is defined as the ratio between grey water footprint value of certain water body and volume of that water body. The improved method can not only describe the distribution of certain pollutant in different water bodies such as river, lake, sea, reservoir and underground water, etc. and demonstrate the combination structure of pollutants in certain water body, but also reflect the pollution severities of different water bodies, so it makes the result more accurate. After empirical analysis of Hunan province with the improved grey water footprint, the following results are obtained: during the years 1985-2013, the grey water footprint increased from 133.0 billion to 224.8 billion cubic meters with a steady annual growth rate of 1.89%, and the grey water footprint of surface water accounted for 70%, while the underground water for 30% approximately. The grey water footprint of surface water was determined by ammonia nitrogen in 1985-1991 and by phosphorus in 1992-2013, while the grey water footprint of underground water was always determined by phosphorus in 1985-2013. During the 29 years, the environment load index of surface water was always lower than that of underground water, and the difference between the two varied from 0.41 to 1.03 then to 0.76 demonstrating an inverted U shape. It means that the environment condition of surface water was better than that of underground water during the research time period, and the gap firstly increased and then decreased.