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Duct climatology over the South China Sea (SCS) was statistically analyzed in the present study based on 10-year ECMWF reanalysis data. The results show that the spatial distributions of the ducting events over the SCS exhibit obvious monthly variation. May is a key time point that separates the spatial distribution pattern of duct characteristics over the SCS. Ducting events often occur in the first half year and higher ducting probabilities are the broadest area of the SCS in March and April. There are two higher ducting probability regions including the northeast and west of the SCS since June. According to seasonal variations, the duct probability, the duct strength and thickness reach their maximum in spring, followed by winter, autumn, and summer. The atmospheric ducts occur more often in the north than south of the SCS and more ducts especially the surface ducts are present off the mainland. The wind field over the SCS plays a very important role in ducting events and the winter monsoon over the SCS allows ducts to form readily in the middle and north SCS until the onset of the summer monsoon. By contrast, the summer monsoon makes it difficult for ducts to form over the SCS. In the monsoon reversal periods, the higher duct occurrence area decreases and less ducts form in most of the SCS.