Abstract: Based on hydrological and meteorological data from Fengyi, Jiangsheba, Weizhou, Zagunao and Shaba stations, combined with ERA5 reanalysis data such as the daily geopotential and wind field provided by the European Centre for Medium-Range Weather Forecasts, the causes of discharge reduction in the Minjiang River Basin under the anomalous high temperature in August 2022 were explored from a synoptic perspective by comparing the discharge differences between August 2020 and August 2022. The results showed that: (1) The discharge reduction in the Minjiang River Basin was correlated with precipitation, both of which were anomalously low in August 2022. (2) In August 2022, the Western Pacific Subtropical High shifted westward and northward. The Minjiang River Basin was obviously controlled by the Western Pacific Subtropical High, which was not conducive to the production of precipitation. (3) In August 2022, the southwesterly wind at 850 hPa over the Minjiang River Basin was weaker than that in normal years. In terms of water vapor transport, the southwesterly moisture transport from the Bay of Bengal was significantly weakened. Furthermore, there was no water vapor convergence in the whole layer of water vapor flux divergence, which made the water vapor conditions in the Minjiang River Basin significantly worse than normal years. (4) The Rossby wave energy dispersed to the mid-to-low latitudes of China, causing the Western Pacific Subtropical High to extend westward and control the Sichuan region, resulting in reduced precipitation over the Minjiang River Basin in August 2022.