The catchment Karuxung was a typical area and unique with a long term observations in the Tibet-Himalayas since 1983. The altitude of the basin varies widely from about 4 550 m to 7 200 m. Owing to higher elevation, the alpine permafrost covers about drainage area of 60%, which limit line is around 5 100 m, above which underlay permafrost and the below is seasonally frozen ground. Mann-Kendall trend analysis, the Sen's slope estimate and correlation analysis were employed to analyze hydrological processes during cold season. The results indicated that the runoff in cold season all have pictured significant increasing trends, of which runoff change in January was the most obvious, which was about 67%. The runoff in January has a high correlation with the runoff from July to December at a significance level of 95%. Therefore, the runoff change in cold season was caused by the former months jointly, which was a characteristic in permafrost region.