Abstract: Protein phosphatase 2C family protein is a class of protein phosphatases that plays an important role in stress resistance. However, there are few studies in crustaceans. In this study, we cloned and obtained the full-length cDNA of protein phosphatase 2C (PmPP2C) with c-type domain in Penaeus monodon by rapid amplification of cDNA ends (RACE). The full length of ORF was 2 079 bp, encoding 692 amino acids. The real-time fluorescence quantitative results show that PmPP2C was expressed in all the tested tissues. The expression was the highest in hepatopancreas and gill tissues, followed by thoracic nerve, testis and muscle. The expression of PmPP2C in hepatopancreas and gill was first down-regulated and then up-regulated under 96 h acute low salt stress. The expression of PmPP2C in hepatopancreas and gill showed a downward-upward-downward trend under 96 h acute ammonia nitrogen stress. The results indicate that PmPP2C can be involved in the response of P. monodon to acute low salt and ammonia nitrogen stress, suggesting that it may play an important role in the immune defense against environmental stress.