Abstract: The Three River Headwaters Region (TRHR) is the most sensitive and fragile area of China's ecosystem. Its precipitation is a key factor affecting water resource security and sustainable development of the ecosystem in this and downstream areas. Using daily precipitation data from 22 national stations in TRHR from 1961 to 2022, the spatiotemporal characteristics and trend changes of precipitation in the region over the past 62 years were analyzed using methods such as MK test, cumulative anomaly analysis, and trend analysis,and its causes were preliminarily explored. The results are as follows. (1) The TRHR precipitation showed significant regional differences, with a spatial pattern of increasing from northwest to southeast, consistent with the decreasing trend of terrain from west to east. (2) The average annual precipitation of the TRHR showed a significant increase trend over the past 62 years, with a turning point around 1990. After 1990, the increase trend of the average annual precipitation had become more significant, with a significant increase in spring, summer, and autumn, and a decreasing trend in winter. The number of heavy rainfall days and precipitation intensity had significantly increased, especially since 1990. (3) The increasing trend of precipitation was mainly in the eastern and southern regions, with some stations in the Lancang River source area and the Yellow River source area showing a longer increase trend. The increase trend was more significant in the river source area in summer, especially in the eastern part of the Yellow River source area where there was a greater increase and a slight decrease in winter. (4) After 1990, The Mongolian high pressure at 500 hPa was enhanced, and the cold air in West Siberia was enhanced. The westerly wind was weakened at 700 hPa, with the easterly wind strengthened. The vertical upward movement was enhanced, and the convergence of the TRHR water vapor flux was enhanced. The simultaneous enhancement of power and water vapor conditions was a possible reason for the increase in precipitation after 1990.