Temperature inversion is an important meteorological phenomenon that affects the diffusion and migration of air pollutants. To forecast air quality accurately, it is essential to understand the characteristics, formation, and dissipation mechanisms of temperature inversion. The sounding data used in this study came from 24 radiosonde stations in northwest China. We systematically analyzed the characteristics of inversions and their effects on air pollution in northwest China. Additionally, we developed a conceptual model of inversion formation mechanisms over the region's complex underlying surfaces. The results indicated that inversions are prevalent throughout the year in northwest China, occurring more frequently at 08:00 Beijing time than at 20:00. The annual average number of inversion days across multiple stations is 330.4 days, with an average inversion strength of 1.20 degrees C/100 m and an average inversion depth of 291.2 m. The spatial distribution of the number of inversion days, strength and depth in the Qinghai-Tibet Plateau region is smaller than that in the Arid region of northwest China and the Eastern monsoon marginal zone. The occurrence of inversions in Northwest China exacerbates air pollution, demonstrating with inversions accounted for more than 70% of the days of occurrence in the daily statistics of air pollution. In particular, SBIs(surface-based inversions) and NSIs(near-surface inversions) have a significant impact on air pollution. Both representative indicators of air pollution, PM 2.5 and O3 concentrations, exhibited parabolic relationships with inversion strength. The PM 2.5 concentration reached its maximum value (108.27 mu g/m3) at an inversion strength of 1.51 degrees C/100m, showing a linear positive correlation with inversion depth and a negative correlation with O3 concentration. The formation of inversions in northwest China is primarily influenced by two factors: the concave topography and the unique geographic environment of the Tibetan Plateau, and the atmospheric circulation. These findings provide a scientific basis for understanding the structural characteristics of inversions in northwest China and for developing strategies to mitigate air pollution.