Abstract: Understanding the variation patterns of hydrogen and oxygen isotopes in ice and water of the Chagannaoer Lake, as well as the recharge-discharge relationships of different water bodies, can provide foundational data for water resource management in this region. Water samples were collected from groundwater wells, lakes, the Gaogesitai River, springs, and reservoirs of the Chagannaoer Lake during the non-ice-covered period (June 2023) and the ice-covered period (January 2024). The study analyzed the variation characteristics of δD and δ¹⁸O isotopes in different water bodies and used the Bayesian mixing model to determine the recharge-discharge relationships at different times. The research results indicated that the mean δD and δ¹⁸O values during the non-ice-covered period were higher than those during the ice-covered period, while the mean deuterium excess (d-excess) was higher in the ice-covered period than in the non-ice-covered period. During the non-ice-covered period, the mean δD and δ¹⁸O values were ranked as follows: lake water > spring water = reservoir water > river water > well water. The mean d-excess values were ranked as follows: well water > river water > reservoir water = spring water > lake water. During the ice-covered period, the mean δD andδ¹⁸O values were ranked as follows: lake water > reservoir water > river water > well water > spring water. The mean d-excess values were ranked as follows: spring water > well water > river water > reservoir water > lake water. The δD and δ¹⁸O in the Chagannaoer Lake exhibited clear stratification during the ice-covered period, with the ranking as follows: ice-covered water (top layer) > ice-covered water (middle layer) > ice-covered water (bottom layer) > non-ice-covered water > ice-covered period water. The ranking for d-excess was as follows: ice-covered period water > ice-covered bottom layer > ice-covered middle layer > non-ice-covered water > ice-covered top layer. The results of the Bayesian mixing model showed that during the non-ice-covered period, the lake water was mainly replenished by precipitation (75.10%), while during the ice-covered period, it was primarily replenished by groundwater (well water 58.32%, spring water 31.45%). The main fate of lake water during the non-ice-covered period was evaporation loss (50.00%), while in the ice-covered period, it was ice formation (45.00%).