Abstract: The nuclear polyhedrosis virus of Clania variegata (CvNPV) and the sysmptom of the disease were observed. The dead larvae caused by CvNPV fall into two categories: one is caused only by CvNPV, the other by CvNPV and bacteria. Eggs of C. variegata were contaminated with different concentration of the polyhedral inclusion bodies (PIB) of CvNPV, the regression equation was obtained between concentration and mortality: y=0. 78 + 0. 832x and LC50=l. 18× 105PIB/mL. Eggs were contaminated with 105, 5×105, 106 PIB/mL, then relationships was got between time and mortality, LT50. They were y=6. 54×-0. 36, LT50=6. 60 days; y = 5.11x+0. 29, LT50= 8. 35 days; y= 4. 93x + 0. 09, LT50 = 9. 91 days respectively.