Abstract: To study the distribution and variation of virioplankton in the sea of raft culture of Pationopecten yessoensis in the Guanglu Island and the Da Changshan,virioplankton abundance was determined by epifluorescence microscopy(EFM).At the horizontal scale,virioplankton abundance in inshore waters including the surface,10 m and bottom layers were higher than those in offshore waters(P<0.05);At the vertical scale,virioplankton abundance of the surface was higher than that of 10 m layer and bottom layer(P<0.05)in the offshore waters.There was no difference between 10 m layer and bottom layer,and there was no vertical difference in the inshore waters between surface and bottom layer.As for the seasonal changes,virioplankton abundance of spring and summer were higher than those of autumn and winter.The virioplankton abundance of summer was highest.According to multi-correlation analysis,virioplankton abundance was distinct positive correlated with the Chl.a(P<0.01)and positive correlated with the temperature(P<0.05).Virioplankton abundance had no significant correlation with salinity and DO(P>0.05).