In order to investigate the non-uniform distribution characteristics of the flood season precipitation and trend, this paper analyzes the temporal distribution characteristics and evolution trend of the flood season precipitation in Jinhua from 1971 to 2020 by using the dayily precipitation data combined with the ECMWF reanalysis data, and by applying the improved index of precipitation concentration and concentration period. The results show that the initial day of the precipitation concentration period during is on June 13, which coincides with the initial day of the monsoon season; Jinhua region generally has a relatively uniform temporal distribution of precipitation, but with large inter-annual variability; and There is a quasi 18-year cycle of precipitation concentration and period of concentration. In the SST field, the anomalously high SST in the east-central Pacific Ocean in the winter before the year of precipitation anomaly concentration, and then the SST difference in the east-central Pacific Ocean at the equator gradually turns into a significant negative anomaly, which suggests that the anomalously concentrated year of precipitation anomaly may occur in the decaying stage of El Ni?o. The most notable anomalies in the situation field are the strong and westerly subtropical high pressure in the western Pacific and the anomalous anticyclone in the Philippine region. Anomalous anticyclones in the Philippine region allow for strong moisture transport from the southwesterly flow along the eastern coast of China during the early summer season, an the same time causing the subtropical high pressure to strengthen and extend westward. The potential gradient between the stronger subtropical high pressure and the westerly trough can increase the transport of warm and humid air from the southwest and slow down the movement of the westerly trough ridge, in order to form a more stable circulation configuration, resulting in the emergence of sustained precipitation. And after the strong subtropical high pressure continues to extend west and lift north, the westerly wind belt system southward is blocked, the large warm high pressure of the sinking air flow will lead to persistent high temperature and drought heat weather, which will lead to an abnormal concentration of precipitation.