Based on the boundary data of lakes, some moderate-high resolution remote sensing datasets including MODIS and Landsat TM/ETM + images and the meteorological data, the spatial-temporal variations of lake ice in the Hoh Xil region during the period 2000-2011 are analyzed by using RS and GIS technology. And the factors affecting the lake ice phenology are also discussed. Some conclusions can be drawn as follows. (1) The freeze-up start (FUS) and freeze-up end (FUE) of lake ice appears in late October - early November, and mid-November - early December, respectively. The duration of lake ice freeze- up is about half a month. The time of break-up start (BUS) and break-up end (BUE) of lake ice is relatively dispersed, and appears in late April - early June, and early May - early June, respectively. The ice duration (ID) and the complete ice duration (CID) of lakes are 196 days and 181 days, respectively. (2) The phenology of lake ice in the Hoh Xil region changed dramatically in the last 10 years. Specifically, the FUS and FUE time of lake ice showed an increasingly delaying trend. In contrast, the BUS and BUE time of lake ice presented an advance. This led to the reduction of the ID and CID of lake ice. The average rates of ID and CID were - 2.21 d/a and - 1.91 d/a, respectively. (3) The variations of phenology and evolution of lake ice are the results of local and climatic factors. The temperature, lake area, salinity and shape of the shoreline are the main factors affecting the phenology of lake ice. (4) The spatial process of lake ice freeze- up is contrary to its break-up process. The type of lake ice extending from one side of lakeshore to the opposite side is dominant in the Hoh Xil region.