Abstract: Cell growth of Nitzschia closterium and Platymonas subcordiformis was stimulated under 4 and 8μg·L^-1 anthrancene stress, respectively. The cell growth of two species was also stimulated under 30mg·L^-1 streptomycin stress. The hormesis of marine microalgae cells under low level of anthrancene and streptomycin resulted in low level of free radical and decrease of microorganisms. Furthermore, the hormesis of marine microalgae was also discussed in this paper.