Abstract: This paper reported the morphological character, ultrastructure of Homona magnanima cytoplasmic polyhedrosis virus(Hm CPV), and its tissue pathological changes, properties of nucleic acid and biological activity, Hm CPV polyhedrosis bodies have a shape of icosahedron or a sphere, its diameter is 0.42~ 2.05μm. The virions have a mean diameter of 42~62nm, it is nearly spherical ,with tubular structure. The concentration of Hm CPV for 5th instar Homona magnanima larvas to determine the LC50 is 3.3 × 106CPB / ml. The LT50 is 10.4 days in the third instar larves infected by concentration of 1 × l06CPB/ml.