Based on the 42 years of data from 1970 to 2020, the traditional statistic methods and random forests have been used to study the influences of the typhoon in the Western Pacific on precipitation in the eastern part of northwest China (33°N-45°N，93°E-110°E，ENWC). The results are as follows. The peak values of the frequency of typhoon and precipitation are both in July, August, and September. The typhoons in the Western Pacific play an important role in the daily mean precipitation during the period of the typhoons (TP) in that month. The location and intensity of typhoons have the most significant influence on the precipitation in July and the location, intensity, and frequency of typhoons all influence the precipitation in August, while typhoons have little influence on the precipitation in September. The influences of typhoons change with location, time, and the level of precipitation. The influences of typhoons are mainly on the second mode of the EOF analysis, the heavy and extremely heavy precipitation, which shows that the typhoons are not the main factors to influence TP and the influence is indirect and nonlinear. The typhoons influence the precipitation by influencing the location and intensity of the ridges and troughs in the mid-latitude, the West Pacific subtropical high, and the vortex in the low-latitude. The model based on the random forests can fit the distribution and intensity better than the linear model, which shows that the influences of typhoons on TP are mainly nonlinear and the nonlinear influence increases with the intensity of the precipitation. The random forests model also shows that the location of the typhoon is the most significant factor to influence the precipitation in ENWC.