Diatoms are an important link in the food chain and a major source for organic matter in marine environments, especially in coastal areas. Chaetoceros subtilis var. abnormis Proschkina-Lavrenko are from coastal areas of Can Gio, Ho Chi lvfinh city and cultured in the f/2 medium at different initial cell densities and under two standing and shake liquid culture conditions. The results shown that the initial cell density 5,000 cells/ml in shake liquid culture condition, the growth of population is the best: the long-chained cells, the larger and darker chromatophores, and having the typical growth curve.