Haemocyte characterization of Chlamys farreri was assayed in this study after injection of the spherical virus isolated from the infectious tissues of the scallop collected in the period of massive death in Jiaozhou Bay. At 8 h, 24 h, 48 h, 72 h and 128 h after injection with spherical virus, population proportion and mortality of haemocytes from C. farreri were assayed by flow cytometry, and effect of virus on haemocyte functions, including phagocytosis and encapsulation in vitro, was studied by fluorescence microscope. The result showed there was significant difference between subpopulation proportion of experimental groups and control. After infection with virus, the hyalinocyte proportion of haemocytes of experimental groups was significantly higher than that of control groups at 24 h, 48 h and 72 h. But the big granulocyte proportion was significantly lower than that of control at 8 h, 24 h, 48 h and 72 h. Mortality of haemocytes of experimental groups was significantly higher than that of control at 24 h, 48 h, 72 h and 128 h. The phagocytosis and encapsulation rate of haemocytes of experimental groups was significantly higher than that of control.