We studied the water level changes of the Yamzhog Yumco Lake from 1974 to 2010 and discussed the factors thatcaused the lake water level changes by comparing the meteorological data from the Langkazi meteorological station with theobserved lake water level changes. We calculated the accumulated anomaly of annual precipitation and annual potential evaporationfrom the meteorological station and compared it with the water level changes of Yamzhog Yumco Lake. The results show that theaccumulated anomaly of annual precipitation had consistency with the inter-annual water level change of the Yamzhog Yumco Lakebefore 2005, indicating a precipitation dominated lake water level change. The combination effect of precipitation and evaporationchanges can account for 93% of the lake level change. From 2005 to 2010, however, the observed lake level deviated from theprecipitation change trend. The study shows that the climate change can not interpret why the water level quickly decrease in thepast years. Probably, the human activity is one of the main factors leading to the water level decrease in the Yamzhog YumcoLake.