Abstract: In this paper, homogenized daily precipitation data collected at 335 meteorological stations in western China from 1971 to 2022 are used to calculate each station's precipitation Concentration Index (CI). By combining the regionally averaged rainfall intensity, number of rainfall days, and the proportion of different intensity rainfall days with statistical methods such as moving averages and the Piecewise Linear Fitting Model (PLFIM), this study analyzes changes in precipitation structure and uneven distribution of autumn rain of West China. The results are as follows. (1) Most stations in West China have a multi-year average CI exceeding 0.6 during the autumn rain period, suggesting that precipitation is not evenly distributed over time at many stations. Further comparative analysis of specific years and stations supports the validity of CI. (2) Over the past decade, temporal inhomogeneity of autumn rain of West China has been gradually intensifying. The direct possible cause is the shift in precipitation structure over the past 20 years, which is characterized by a decrease in the proportion of light rain and an increase in the proportion of heavy rain and extreme precipitation. The rise in intense rainfall has led to greater precipitation concentration, thereby enhancing the temporal inhomogeneity of precipitation distribution.