In the context of global climate change, China has experienced frequent occurrences of extreme precipitation and extreme drought events. However, there has been limited reporting on the changes in precipitation grade transitions and the periodic shifts in the center of gravity of precipitation across the mainland. Revealing the spatiotemporal patterns of long-term precipitation is of significant importance for preventing natural disasters such as floods and droughts, and for promoting regional sustainable development. Based on the annual precipitation data synthesized from monthly precipitation data in China, this study employs methods such as the center of gravity model, transition matrix, mutation analysis, trend analysis, and others to analyze and explore the spatiotemporal characteristics and periodic patterns of precipitation across different time scales and regions in China from 1901 to 2022. The findings indicate that: (1) The precipitation isopleths trend northeast-southwest, with precipitation decreasing from the southeastern coastal areas to the northwestern inland regions. The semi-humid zone covers the largest area, accounting for 28.96%, while the humid zone covers the smallest area, accounting for 13.77%. (2) From 1961 to 2022, compared to the period from 1901 to 1960, the national precipitation isopleths have gradually shifted from the southeastern coastal areas to the northwestern inland regions. (3) The Southwest River basins region experienced the largest decrease in precipitation, approximately -1.94 mm/a, showing a fluctuating decreasing trend. The Huai River Basin showed a significant increasing trend in precipitation, with an increase of about 4.12 mm/a, indicating a fluctuating increasing trend. The Yellow River basin exhibited relatively stable precipitation changes. (4) The center of gravity of precipitation in different regions shows certain spatial heterogeneity. The Liaohe River basin has the smallest standard deviation ellipse area for the center of gravity, indicating the least dispersion and suggesting smaller overall differences in precipitation across the region. The Haihe River basin's center of gravity generally follows a triangular pattern of change. The Northwest River basins region shows a north-south periodic change in the center of gravity, indicating significant precipitation changes in the north-south direction. The Pearl River basin's center of gravity shows a west-east periodic change, indicating significant precipitation changes in the west-east direction. (5) From 1900 to 1960, the national precipitation trend was relatively stable. From 1961 to 2022, precipitation significantly increased, ultimately showing a trend of shifting from lower to higher precipitation grades. The results of this study can provide theoretical support and decision-making basis for policymakers in developing protection and development systems for different river basins.