An effective method for cell harvesting of the halotolerant microalga, Dunaliella tertiolecta ATCC30929, was investigated. By increasing the, pH of the culture broth using NaOH solution, suspended D. tertiolecta cells rapidly coagulated and settled within a few minutes, which Allowed simple harvesting of the concentrated cells from the culture broth. The pHs for successful coagulation were between 8.6 and 10.5 and more than 90% of cells was recovered from the culture broth. Clarified culture broth could be reused for the successive cultivation of D. tertiolecta simply by supplying fresh medium and neutralizing alkali with HCl without the requirement for an additional inoculum.