Abstract: This study was aimed to analyze the PDI-2 protein of Haemaphysalis longicornis by using bioinformatics software and to predict possible epitopes of its B cells and T cells. The physicochemical properties of the protein were analyzed by ProtParam; the secondary structure and tertiary structure of the protein were predicted by SOPMA and SWISS-MODE; the B. cell epitope was predicted by IEDB and BepiPred; and the T cell epitope was predicted by SYFPEITHI. After comparison, the protein formula of long-horned blood clam PDI-2 is C₂₅₃₈ H₃₉₆₆ N₆₅₄ O₇₉₅ S₁₇,the theoretical isoelectric point was 4.85, and there were three transmembrane regions. PDI-2 contained 13 regions with a high hydrophilicity parameter score of ≥1.9, 11 regions with a flexibility parameter score of ≥2.0, and 11 regions with a surface accessibility parameter score of ≥1.9. The protein contained 20 post-translational modification sites, with α-helix of 42.69%, β-sheet of 19.44%, β-turn of 5.01%, and random curl of 32.87%. There were 20 CTL dominant epitopes, 3 dominant epitopes and 23 B cell dom inant epitopes. After analysis and comparison, PDI-2 protein was rich in antigenic epitopes, providing a scientific theoretical basis for the study of aphid vaccines.