Herbicide tertbutyl triazine was used for removal and control of red tide caused by Phaeocystis globosa and Alexandrium tamarense under laboratory condition. The results showed that the effective concentration of tertbutyl triazine for killing P. globosa and A. tamarense was 0.3 mg L-1 and 0.2 mg L-1, respectively, for 96 hours. Tertbutyl triazine might be a good algaecide with high efficiency and durative action.