North west China is a typical arid and semiarid region. Due to the constraints of natural factors such as climate, and hydrology, the natural conditions are harsh and the ecosystem is relatively sensitive. Compared with other provinces and regions, the urban comprehensive carrying capacity is more fragile, scientific and reasonable evaluation of the urban comprehensive carrying capacity is of great practical significance to urban sustainable development. In this paper, nine indicators are selected from the four aspects of population, economy, construction and transportation to construct the evaluation index system of the urban comprehensive carrying capacity. Entropy weight method (EWM) and linear weighted sum method are used to calculate the urban comprehensive carrying capacity of the five provinces in Northwest China in 2020, and the classification and spatial differentiation analysis are carried out. Ordinary least squares (OLS) and geographically weighted regression (GWR) were used to analyze the influencing factors of the urban comprehensive carrying capacity in Northwest China. Results indicated that: The overall level of the urban comprehensive carrying capacity in northwest China is relatively low and its spatial distribution is extremely unbalanced, showing the spatial distribution characteristics of Xi'an, Urumqi and Lanzhou as 'three cores', and forming positive radiation effect on the surrounding areas. Per capita GDP, population density, per capita construction land area and road network density are the main factors affecting the urban comprehensive carrying capacity in this region, and all play a positive role in improving the urban comprehensive carrying capacity.