Farnesoic acid O-methyl transferase (FAMeT) is the enzyme that catalyses methylation of farnesoic acid (FA) to produce isoprenoid methyl farnesoate (MF) at the final step of the biosynthetic pathway. As a sesquiterpenoid analogue of the insect juvenile hormone (JH), MF has been suggested to play a vital role in regulating crustacean growth and reproduction. In this study, the full-length FAMeT cDNA (GeneBank accession number: KC192659) of P. trituberculatus is cloned, it contains a 201bp 5-untranslated region(5-UTR), a 318bp 3-untranslated region (3-UTR) and a 825bp opening reading frame, which encodes 274 amino acid residues. Alignment of deduced amino acid sequence with FAMeT amino acid sequences of other crustaceans revealed that it shares the highest identity with P. Pelagicus among the identities ranged from 75% to 97%. The amino acid residues consist of two copies of CF (CPAMD8/FAMeT) domain, which are the hallmark domain of FAMeT and are present in all crustacean FAMeTs. Realtime PCR was used to quantify the relative expression level of FAMeT in different tissues and molting stages in P. trituberculatus. The results showed that FAMeT was expressed in various tissues. The mRNA level of FAMeT was highest in Taoracic ganglia, followed by gill and mandibular organ (MO). During the molting process, the expression of FAMeT in MO increased to the maximum at D1 stage, then gradually decreased to the minimum at D4 stage. The results suggest that FAMeT plays an important role on molting regulation in P. trituberculatus.