Abstract: To quantitatively analyse the influence of climate change and human activities on Honghu Lake, the water surface area of Honghu Lake was extracted using multi-temporal remote sensing imagery including Landsat MSS, TM, ETM+ and HJ-1 CCD from the 1970's onward. Regression analysis was used to obtain relationships between lake area and precipitation, precipitation days, and evaporation. The results show that there was a relatively large difference in lake area between different years and the area decreased over 40 years, especially in the middle and late 2000's. The area was influenced by precipitation, and the decreasing number of precipitation days had negative implications for Honghu Lake water levels. Increasing human activity contributed to a reduction of lake area. The regression coefficients of climate and human activities to lake area were 0.78 and 0.50, respectively, which suggests the impact of climate change on the lake area is greater than the impact of human activities. However, the impact of human activities on lake area has gradually increased in recent years. Less precipitation and the expanding influence of human activities are the main causes of the reduced area of Honghu Lake in the middle and late 2000's.