Abstract: Isochrysis zhanjiangensis was preserved in liquid nitrogen by encapsulation-vitrification. The followingfactors affect the viability of the alga such as the composition and the concentration of loading solution and loading time, the time of dehydration, the concentration of washing solution and washing time were studied. The result showed that the high viability of 54 % was obtained when the beads containing the algal cells were loaded with 50 % PVS(PVS:30 %(W/V) glycerol, 20 %(W/V) ethylene glycol and 10 %(W/V) dimethyl sulfoxide inf/2 medium)for 4.5h at 20 ℃, then dehydrated with 100 % PVSfor 50 min at 0 ℃ prior to a direct plunge into liquid nitrogen and washed by 1mol/L sorbitol for 40min after warming in 40 ℃water bath. The method of encapsulation2vitrification do not need special equipments, simplifies the operation procedure of cryopreservation, so it is a potential method for preservation of I. zhanjiangensis and other algae.