Antheraea pernyi nucleopolyhedrovirus (ApNPV) p11 gene is 309 bp long, potentially encoding 102 amino acids with a predicted molecular weight of 11.2 kDa. ApNPV p11 gene was cloned into the prokaryotic expression vector pQE-30 and P11 was expressed in E. coli M15. Polyclonal antiserum was made against 6xHis tagged P11 protein expressed in E. coli M15. P11 gene transcription was detected as early as 36 h post-infection (p.i.) in tussah pupa and remain at high level up to 96 h p.i. Structural localization revealed that P11 protein was present in polyhedral inclusion bodies (PIB) dilute alkaline saline (DAS) pellet (P) fractions and occlusion-derived virus (ODV), but not in PIB DAS supernatant (S) fractions and budded virus (BV). These results indicated that P11 was associated with ApNPV structure.