It is important to study the characteristics of precipitation anomaly in the Beijing-Tianjin-Hebei region to improve the understanding and prediction ability of precipitation in the autumn extended period. In recent years, the phenomenon of“ summer rain in autumn” has occurred frequently in the Beijing-Tianjin-Hebei region, showing the characteristics of precipitation intensity increase and more extreme precipitation in autumn. The autumn precipitation in the Beijing-Tianjin-Hebei region in 2021 was the most since 1981, and the precipitation at many stations in October of 2021 broke the historical extreme values. Based on daily precipitation data in autumn and NCEP/NCAR reanalysis data in Beijing-Tianjin-Hebei region, the Morlet wavelet analysis and Lanczos filtering methods were used to analyze the low-frequency oscillation period of autumn precipitation and the evolution of atmospheric low-frequency circulation characteristics in the Beijing-Tianjin-Hebei region in 2021 in order to explore its abnormal characteristics. The results show that the main low-frequency oscillation period of autumn precipitation in the Beijing-Tianjin-Hebei region in 2021 is 10-20 days, and the variance of low-frequency oscillation is 44%. The low frequency circulation at 500 hPa during the low frequency precipitation activity period shows that there is convergence movement before the low-pressure anomaly, which is conducive to the strengthening of the low-level anomaly cyclone and upward movement. During the low frequency precipitation activity period, an abnormal cyclone moves northward from the South China Sea to the Beijing-Tianjin-Hebei region, which was conducive to the transport of warm and humid air from the south to the Beijing-Tianjin-Hebei region. The intensity of water vapor transport will affect the intensity of precipitation process. The stronger the intensity of water vapor transport is, the greater the intensity of precipitation is.