Based on the ERA5 hourly reanalysis dataset and the merged hourly precipitation products from National Meteorological Centre from May to June from 2010 to 2016, the low-level jet events affecting South China were selected and classified using an objective method.This paper also investigated the diurnal cycles of boundary layer jet (BLJ) and synoptic-system-related low-level jet (SLLJ) during early-summer, and analyzed their influences on temporal and spatial distributions of diurnal cycle of precipitation in South China.Results show that BLJ and SLLJ weaken during the day and increase at night, and reach the peak in the early morning.Their diurnal cycles are mainly related to the clockwise rotation of ageostrophic winds caused by inertial oscillations of boundary layer.The precipitation in South China increases significantly during the double low-level jet days, and the diurnal cycle of precipitation has obvious regional differences, which is closely related to the evolution and configuration of the double low-level jets.The precipitation in central and northern Guangxi is mainly concentrated over the mountainous area at the left anterior to the SLLJ at night and is characterized by only one single peak in the early morning.There are two peaks in the morning and afternoon in coastal Guangxi and Guangdong.The maintenance of convergence in BLJ exit area and divergence in SLLJ inlet area are conducive to the increase of precipitation frequency, resulting in the emergence of afternoon peak.In addition to the influence of the favorable configuration of the double low-level jets, the morning peak of precipitation is mainly due to the increase of the morning precipitation intensity.