Abstract: To forecast winter runoff under future climate change, the Cold Region Hydrological Model (CRHM) platform was applied to simulate the winter runoff volumes during 2000—2012 and forecast the winter runoff volumes during 2025—2060 of upper reach of Yijimi River, a secondary tributary of China's Songhua River. The results indicate the following. ① Based on the changes of annual winter runoff depth and runoff coefficient during 2025—2060, the instability of winter runoff series would increase with increasing representative emission concentration. ② On the basis of location identification of mutation points, the higher the representative emission concentration, the greater the inflection point of accumulated winter runoff. ③ According to the correlation analysis, the climate in the same period is the main factor affecting monthly runoff in winter, and winter precipitation is the main factor affecting the changes of winter monthly runoff. ④ By comparison of cumulant slope changes, compared with the period 2025—2042, the contribution rates of winter precipitation growth to winter runoff growth during 2043—2056 and 2057—2060 are 39.8% and 62.6%, respectively. Compared with the period 2043—2056, the contribution rate of winter precipitation reduction during 2057—2060 to winter runoff reduction is 27.0%.