This study aims to evaluate the accuracy of the atmospheric precipitable water vapor (PWV) inversion using the Global Navigation Satellite System (GNSS) technology and its temporal-spatial distribution characteristics in the central and western regions of the Chinese mainland. By comparing PWV data from 15 GNSS stations with ERA5 reanalysis data and radiosonde data, this paper analyzes the precision and consistency of GNSS-based PWV inversion, discusses the influence of latitude, elevation, and climatic factors on the accuracy of PWV inversion, and finally reveals the temporal-spatial variation patterns of PWV. The results indicate good consistency between GNSS PWV and radiosonde PWV, demonstrating the high reliability of GNSS in PWV measurement. The PWV inversion accuracy is closely related to the geographical location of the sites, with the mean absolute error and root mean square error increasing with latitude and decreasing with elevation. The temporal-spatial analysis reveals a growth trend of PWV at 0.12 mm/year, along with significant annual, semi-annual, and 1/3-annual cyclical signals, and the spatial distribution closely related to topography and climatic conditions. The study confirms the high reliability of GNSS-based PWV inversion, analyzes the significant influence of site geographical characteristics on accuracy, and lays a solid foundation for the extensive application of the GNSS technology in climate change monitoring and atmospheric water vapor research.