Owing to the fact that the objective identification methods of rainy season are not totally identical in the three provinces of Northeast China, no unified monitoring criterion of rainy season is available in this area. In order to implement the regional key climate monitoring and to meet the needs of the national weather service, from the angle of the whole region, based on the daily precipitation data of 102 observational stations, by comprehensively analyzing the daily precipitation series disposed by 5-point moving average, the objective identification method of midsummer rainy season in the northeast China is presented in this paper. Then based on the daily reanalysis data of wind field and geopotential height field provided by NCEP/NCAR, the atmospheric circulation fields of different levels before, during and after the midsummer rainy season are contrastively analyzed, and the rationality of the objective identification method is validated. Finally, the partition criterion of the beginning and ending dates are determined. Results show that: the average beginning and ending dates of midsummer rainy season in the northeast China respectively are June 26th and August 30th. The partition criterion of midsummer rainy season in the northeast China by using the objective identification method is reasonable.