The impact of climate change on lakes is one of the lake research foci. As the largest freshwater lake in Eurasia, Lake Baikal is impacted by both the natural environment and human activities. Hence, it is indispensable to discuss how Lake Baikal will change with global warming to guarantee the watershed ecological balance and regional sustainable development. We, therefore, analyzed the climate change in the Lake Baikal region and its impacts on the water surface level of Lake Baikal over the past 40 years, with the coefficient of variation test and multi-methods of abrupt change test using the observation data from meteorological stations, hydrological stations and water level of the lake surface. The main conclusions are summarized as follows. From 1980 to 2019, the annual average temperature around Lake Baikal shows a significant rising trend of 0.31℃/10 a, and its spatial distribution is mainly affected by latitude and altitude. The annual average precipitation fluctuates remarkably with a variation coefficient of about 0.2, and the overall variation trend is not significant. The main controlling factor of its spatial distribution is topography. In the past 40 years, Lake Baikal's average water level is 456.42 m, and the water level has undergone several sharp changes. The runoff in Selenga River and Angara River increases first and then decreases during 1980-2015, leading to the water level changes of Lake Baikal synchronously. The results of path analysis show that precipitation is the main meteorological factor affecting the water level of Lake Baikal. Precipitation affects the water level of Lake Baikal through both direct recharge and runoff recharge. We roughly divide the causes of water level transition into three categories. The first type is the climate change-driven type, which refers to the abrupt changes in water level during 1982-1983, 1985-1987, and 2013-2015. The second type is the combination of climate change and anthropogenic activities. Taking the dramatic decline of water level in 1995-1996 as an example, climate change and the increase of human water use in the basin led to the dramatic shift in water level. The third type is government regulation control with climate change, which is unique to Lake Baikal. That is, the government regulates the water level of the lake artificially through the downstream hydroelectric facilities. Due to the continuous warm and dry climate conditions, Lake Baikal's water level is strictly controlled at a low value of 456.07 m from 2015 to 2017. This study hopefully will provide theoretical support for the projection of climate change, water level control, and disaster prevention of Lake Baikal Basin.