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An objective method is used to identify the Southern Branch Trough (SBT) activity by means of the NCEP/NCAR daily reanalysis dataset from 1981 to 2017. Based on the daily SBT activity and the precipitation data from 156 national observation stations in Sichuan, the temporal and spatial distribution characteristics of SBT and its impact on Sichuan precipitation are investigated. The results show that SBT appears 47.9 times per year and the monthly distribution is bimodal, with the highest frequencies occurring in January and May. The most frequent activitive area is around 90°E and 22° to 24°N, to the south of the QinghaiXizang Plateau and north of the Bay of Bengal. SBT usually enhances from November to January. The intensity of SBT generally decreases with increasing longitude, but there are enhanced areas near 86°E and 96°E. About 73.97% of SBT activities will produce precipitation processes in Sichuan, with the high frequency areas located in the southeast and south parts of the basin. When the South Branch is westward, Sichuan is more prone to precipitation. However, precipitation processes with weaker SBT intensity are generally heavier.