Coccolithophorids in the northeastern and central South China Sea (SCS) were surveyed in March and October 1996. The cell density of coccolithophorids ranged from 25 x 103 cells L-1 to 31 x 103 cells L-1 in sea-surface water (0–25 m in depth), and from 12 x 103 cells L-1 to 62 x 103 cells L-1 in subsurface water (150 m in depth). The lowest cell number was recorded in the subsurface (150 m in depth) in the central gyral area, while the highest one was at the same depth in the northeastern realm. A total of thirty-one species were identified. The species richness in the northeastern SCS is higher than in the central area. Emiliania huxleyi (Lohmann) Hay et Mohler, Gephyrocapsa oceanica Kamptner, Umbellosphaera Paasche spp. And Syracosphaera Lohmann spp. Dominated the surface assemblages, whereas Florisphaera profunda Okada et Honjo, Gladiolithus flabellatus (Halldal et Markali) Jordan et Chamberlain predominated in the subsurface layer. In contrast, Palusphaera vandeli Lecal emend. R. E. Norris presented in both surface and subsurface assemblages.