Abstract: In order to reveal the variation characteristics of Hulun Lake area and identify its primary influencing factors in the past 60 years, the Hulun Lake area from 1961 to 2018 and the annual temperature, precipitation, evaporation and relative humidity of the surrounding area were analyzed using Mann-Kendall tests, linear regression and wavelet analysis. The correlation between the lake area and the meteorological elements was analyzed using Pearson correlation and grey relational analysis. The results showed that the Hulun Lake area (1739-2360 km²) decreased significantly during 1961-2018 at a rate of 72.84 km²/(10 a). Since the implementation of the water diversion project in 2009, it increased gradually and stabilized at 2030 km² in recent several years. The climate of the Hulun Lake area tended to be warmer and drier in the past 60 years, which manifested that the temperature and evaporation increased significantly, the relative humidity decreased significantly, and the precipitation decreased insignificantly. The Hulun Lake area during 1961-2018 showed a corresponding response to the abrupt and periodic changes of the climate. Moreover, the lake area was negatively correlated with the evaporation with a Pearson correlation coefficient of -0.546, and the grey relational coefficients between the lake area and the evaporation and precipitation were as high as 0.938-0.960. The correlation between the lake area and the meteorological elements during the period before the implementation of the water diversion project (1961-2008) was stronger than that during 1961-2018. The increase in evaporation caused by the climate change is the main reason for the decrease in the Hulun Lake area. The water diversion project started in 2009 has a strong impact on the response of the Hulun Lake area to the climate change during 2009-2018.