Ice thickness is an important physical parameter of a lake in the freezing period. It is of great theoretical and practical significance to understand the spatiotemporal characteristics of lake ice, which helps study how lake ice responds to climate under the background of global warming. Based on the ERA5 Climate Reanalysis temperature dataset, MODIS MOD09GQ data product, and ice borehole and radar thickness measurements in 2019, the thickness of lake ice in Lake Qinghai between 2000 and 2019 was reconstructed and the spatial-temporal variation characteristic was analyzed. The results showed that the average growth rate of ice thickness in March (0.30 cm/d) was faster than that in February (0.12 cm/d) based on the field survey data. The average growth rate of ice thickness in Lake Qinghai from November 2018 to March 2019 was 0.34 cm/d simulated by the degree-day model, with the ice thickness error of ±2 cm compared with the actual observation data. However, the error was large at the entrance of the river and the south side of Lake Qinghai. Meanwhile, the simulation of ice thickness was overestimated before the mid-March but underestimated later. The annual average ice thickness of Lake Qinghai was 32-37 cm, in which, it fluctuated dramatically in 2008-2016, showing the tendency of thickening first, then stabilizing and finally thinning. At the beginning of lake freezing, the ice thickness increased rapidly with the growth rate of 0.45 cm/d in December and 0.41 cm/d in January. After February, the rate slowed down, and it was 0.29 cm/d in February and 0.14 cm/d in March. On the whole, the ice thickness of Lake Qinghai showed a spatial pattern of being thicker in the north and east, whereas being thinner in the south and west, years of spatial change were more stable in the west than in the east. The average thickness of lake ice was positively correlated with complete freezing duration and the freeze-up period.