Abstract: Based on the daily precipitation observation data of national meteorological station and agricultural reclamation meteorological station in Sanjiang Plain during 1961-2019 and NCEP/NCAR data, the climate change characteristics and influencing factors of heavy rainfall days in summer in Sanjiang Plain were analyzed. The results showed that the interannual variation of the number of heavy rainfall days in summer in Sanjiang Plain was significant, and the spatial difference of its mean distribution of climate was obvious. In recent 60 years, the number of summer heavy rainfall days showed an increasing trend, in which the most 10.7 days（1994） was 8.6 days more than the least 2.1 days（1977）. During 1961-2019 there were more years in which the number of heavy rainfall days in summer less than the climatic average, and fewer years in which the number of heavy rainfall days in summer more than the climatic average. The strong Okhotsk Sea High was favorable to more summer heavy rainfall days in Sanjiang Plain, while the weak Okhotsk Sea High was favorable to less summer heavy rainfall days. In the abnormal years of summer heavy rainfall days in Sanjiang Plain, the upperlevel jet stream in middle and high latitudes was different. The stronger upper-level jet stream in August was conducive to the more summer heavy rainfall days in the Sanjiang Plain. The intensity and location of the Western Pacific Subtropical High in June, July and August were different in anomalous years of summer heavy rainfall days in Sanjiang Plain.