Abstract: By using the D2 cloud climate datasets from the International Satellite Cloud Climatology Project (ISCCP), NCEP reanalysis data and Nino3.4 SST data, we analyzed the spatiotemporal distribution characteristics and possible reasons of the annual average of the low cloud amount over the South China Sea (SCS), its seasonal circulation as well as its interannual variation. The results show that the annual average climatological state of low cloud amount exerts a northeast to southwest belt-like distribution. In particular, the high value area is located along the coastline of the land-sea boundary. From the perspective of time series, prior to 2001, the fluctuation range of low cloud amount index over the SCS was relatively large, while it went the opposite from 2001 to 2007. The distribution of low cloud amount over the SCS has remarkable seasonal feature, which is related to the onset of summer monsoon and winter monsoon over the SCS. The interannual variation of low cloud amount over the SCS is minimal in summer (June to August) and peaks in winter (December to February). On the interannual time scale, the oscillation period of seasonal variation of low cloud amount over the SCS is 2 to 5 years, which coincides with the period of the ENSO cycle. This finding evidences the correlation between the two. In autumn, the interannual variation of low cloud amount over the SCS is closely related to the El Ni?o phenomenon. The occurrence of El Ni?o is accompanied with increased low cloud amount over the SCS.