Phytoplankton sinking rate in the South China Sea (15°~22°N,114°~120°E) was studied during summer 2017. We found that phytoplankton had a total of 186 species and were mainly composed of diatoms. The main dominant species of phytoplankton were Trichodesmium thiebaultii, Prorocentrum lenticulatum, Thalassionema nitzschioides, Prorocentrum minimum, Thalassiosira minima, Navicula spp., Thalassionema nitzschioides and Prorocentrum compressum, respectively. Phytoplankton sinking rate in the 200m layer of the surveyed area was the highest, followed by the 5m layer, however, the deep chlorophyll maximum (DCM) layer had the lowest sinking rate. As to carbon sinking flux, the 5m layer of which in studied area was the highest, while the DCM layer was the lowest. The carbon sinking flux in 5m layer ranged 0.105 mg C m^-2 d^-1 to 40.690 mg C m^-2 d^-1, with an average of 13.00 mg C m^-2 d^-1. While in the DCM layer, they were between 0.186 mg C m^-2 d^-1and 5.097 mg C m^-2 d^-1, with the average of 2.09 mg C m^-2 d^-1. Consequently, these studies revealed that the sinking of phytoplankton cells was an important pathway for carbon export from the upper layer to the bottom layer, which provided an useful insight into the process of carbon cycling in the South China Sea.