The uncertainty of the probabilistic distribution of precipitation extremes over Xinjiang during 1961-2014 was discussed by using multi-function method. Results suggest that precipitation extremes easily occur in Xinjiang against the background of the climate change from warm-dry to warm-wet, which could take impact on the fitting of precipitation extremes. The uncertainty exists in the selection of functions and extreme estimations. In order to reduce the uncertainty, its suggested to apply the composite analysis with results of GEV, Gen. Logistic, Log-Pearson 3, Pearson 6 and Wakeby functions, when the study is conducted over the whole Xinjiang. For the single station analysis, the compositive curve graph with boundary of the extreme values is suggested to be provided.