Prophenoloxidase, a member of the serine proteinase group, is a key enzyme in invertebrates for defense against microbial infections and the prophenoloxidase activating enzyme (PPAE) is an important component of the prophenoloxidase activating system (PPOAS). A fulllength cDNA of the PPAE gene named PcPPAE (GenBank: KC136292) was cloned from Panonychus citri (McGregor) using rapid amplification of cDNA ends (RACE). The cloned gene was 1 676 bp in length with an ORF of 1 377 bp encoding 458 amino acid residues. The protein predicted from the cloned PcPPAE had a molecular weight of 49.9 ku and a theoretical isoeletric point (pI) of 5.68. Its predicted molecular formula was C2201H3467N607O678S22. Bioinformatic analysis showed that its instability index was 41.51 and its GRAVY was -0.268. The deduced protein PcPPAE had a clipdomain, serine proteinase domain and a conserved catalytic triad in the serine protease domain. Phylogenetic analysis indicates that PcPPAE is most closely related to the clipdomain serine proteinase of Tetranychus urticae (Koch). These results provide the basis for further research on defense against microbial infection in the citrus red mite.