Abstract: Low frequency hearing gene PMCA2 plays an important role in biological hearing, and mutation or deletion of PMCA2 gene may cause neurological deafness and balance dysfunction. In order to explore the role of low-frequency hearing gene PMCA2 of Onchidium reevesii in tidal perception, full-length cDNA of PMCA2 gene in O. reevesii was cloned by RACE technology and phylogenetic analysis was conducted. O. reevesii was divided into two groups: temporary care without treatment group and tidal interference stimulation group. Real-time fluorescence quantitative PCR（RT-qPCR） and in situ hybridization were used to analyze the relative expression levels of PMCA2 gene in each tissue and the relative expression sites in each ganglia of nerve tissue in the two groups. The results showed that the full sequence of PMCA2 gene was 5 091 bp and encoded 1 208 amino acids,which contained 492 bp 5’ noncoding region（UTR）, 972 bp 3’ UTR and 3 627 bp open reading frame. Sequence analysis showed that the homology of PMCA2 amino acid sequence of O. reevesii with that of Aplysia californica,Elysia chlorotica and Pomacea canaliculata were 81.79%, 78.25% and 72.91%, respectively. The phylogenetic tree analysis showed that the phylogenetic relationship between O. reevesii and Aplysia californica was relatively close.RT-qPCR results showed that the expression of PMCA2 gene in nerve tissues of O. reevesii in the two groups was higher than that in other tissues. The expression level of tidal interference stimulation group was significantly higher than that of temporary care without treatment group, with significant difference. The results of in situ hybridization of nerve tissue in the two groups showed that the hybridization signal of nerve tissue in the tidal interference group significantly enhanced compared with that in the temporary care without treatment group, which was consistent with the results of fluorescence quantitative PCR. The bioinformatics characteristics of PMCA2 gene, the expression of PMCA2 gene in various tissues and the distribution of PMCA2 gene in nerve tissues were preliminarily described in the experiment, which provided an original achievement for the study of tidal sensing ability of organisms in tidal area.