The apoLp-III in the adult hemolymph of Artogeia rapae can associate reversibly with lipophorin. The apoLp-III was purified from the adult and larval hemolymph by KBr densitygradient ultracentrifugation, gel permeation chromatography anion exchange chromatography and preparative electrophoresis (Prep Cell). ApoLp-I, ApoLp-II and apoLp III have the molecular weights of 212 kDa, 80 kDa and 18 kDa, respectively. N-terminal sequence of apoLp-III were determined. The N-terminal amino acid sequence of apoLp-III shows 50-57% identity with those of other lepidopteran insects. apoLp-III has the antibacterial activity. Injection of bacteria increase the concentration of apoLp-III in the hemolymph, indicating that apoLp-III plays a role in insect immunity. Immunological analysis was also investigated with the anti-apoLp-III.