Abstract: There are many lakes in the northern Tibetan Plateau, but no lake water level records, except Zabuye Salt Lake, where a long-term field observatory station was established in 1990 by Open Laboratory of Saline Lake Water Resources and Environment, Chinese Academy of Geological Science, and water level was recorded monthly. This is the first time we publish the observing data of the water level fluctuation. According to the lake level records from January 1991 to December 2003, we established a time-serial model for the water level fluctuation of Zabuye Salt Lake, Tibet, and studied the long-term trend, seasonal fluctuation and cycles of the water level changes. Our research reveals that the seasonal fluctuation of the water level during 1991-1996 shows a monomodal pattern, indicating the prominent influence of the thaw of frozen soil and snow/glaciers on the water level, and the water level fluctuation during 1997-2003 shows a bimodal pattern, indicating the increasing influence of the rising air temperature and precipitation in addition to the recharge of thawing water of frozen soil and snow/glaciers in these years. The cyclic period of water level changes is 8.2 years, which is synchronous with the sunspot cycle. The water level generally rose 0.25 m during 1991-2003, but in many of the years the water level showed a long-term trend of dropping by 0.06-0.08 m per year, only in 1992,1997 and 1998 did the water level rise rapidly by 0.18 m per year. The very strong ENSO event occurring during 1997-1998 marked a turn from the monomodal to bimodal pattern of the seasonal water level fluctuation.