Removal and control of Phaeochystis globosa cells by sodium dichlorinated isocyanuric acid and tri-chloroisocyanuric acid were studied. Removal efficiency of the two algaecides was contrasted and removal mechanism was also discussed. The results suggest both of the algaecides have excellent ability to remove and control Phaeochystis globosa cells. Hypochlorous acid is released slowly by the two algaecides and maintains it's stabilization. The effective concentration of available chlorine is 4.5 mg/L. The removal efficiency is more than 90% within 24 hours at the available chlorine's dosage of 5.0 mg/L. Trichloroisocyanuric acid could remove Phaeochystis globosa cells more effectively than sodium dichlorinated isocyanuric acid when concentration of available chlorine was more than 5.0 mg/L. The conclusion was identified by t test of available chlorine and removal efficiency.