Based on the observations and the regional climate model (RegCM4.6),this paper analyzes the possible effects of synoptic scale disturbances at mid-high latitudes and low latitude on the precipitation of Meiyu period in 2020.The observation analysis shows that in June and July of 2020,the precipitation in the middle and lower reaches of the Yangtze River shows a synoptic scale disturbance of less than 10 d in the period,and there are many times of synoptic scale disturbances in middle and high latitudes (low latitude) propagating southward (northward).On this basis,the side boundary sensitivity experiments are designed to change the input of synoptic scale disturbances (<10 d) at different latitudes.Numerical simulation results show that from the perspective of average circulation,when the synoptic scale disturbances on the northwest boundary of middle and high latitudes weaken,the conversion position from the kinetic energy of atmospheric average circulation to the kinetic energy of synoptic scale disturbance moves northward,which affects the northward movement of the westerly belt on the north side of the subtropical high,and makes the precipitation center move northward from the middle and lower reaches of the Yangtze River to the Huaihe River Basin during the Meiyu period.From the perspective of time evolution,when the synoptic scale disturbances on the northwest boundary of middle and high latitudes is removed,the southward propagation of E vector divergence at 850 hPa weakens,and the low latitude zonal wind anomaly can propagate to the north.The vorticity change caused by zonal wind anomaly is beneficial to the northward uplift of subtropical high,which makes the rain belt move northward to the north of 34°N earlier,marking the end of Meiyu season in Jianghuai region.However,when the synoptic scale disturbances on the south boundary of low latitude weaken,the precipitation increases lightly,but there is little influence on the advance and retreat of rain belt during the Meiyu period.It can be seen that the intensity of precipitation and the maintenance of rain belt during the Meiyu period in the summer of 2020 are closely related to the synoptic scale disturbance anomalies in the middle and high latitudes.The strong synoptic scale disturbances in northern China,especially from Northwest China to Lake Balkhash,and its southward propagation are the important reasons for the strong intensity of the Meiyu precipitation and the maintenance of the rain belt.