We evaluated the effect of changes in salinity on four genes involved in salinity regulation (glycine transporter, zinc finger protein, heat shock protein 70, neuronal acetylcholine receptor) in Apostichopus japonicus using real-time quantitative PCR. The basal level of glycine transport gene expression was highest in the respiratory tree, followed by intestinal tissue and coelomic fluid. The level of zinc transporter and acetylcholine receptor gene expression was highest in the coelomic fluid, and expression was not detected in the respiratory tree. Expression of the Hsp70 gene was highest in the coelomic fluid, followed by the respiratory tree and intestine. Exposure to low salinity stress resulted in changes in glycine transporter gene expression in all tissues. Expression peaked in the intestine and respiratory tree after 72 h and 1.5 h, respectively. Conversely, expression in coelomic fluid decreased and was at its lowest level after 3 h. Expression of the zinc transporter gene also changed in response to low salinity stress. Expression peaked after 24 h in the intestinal tissue and after 6 h in the coelomic fluid. Neuronal acetylcholine receptor gene expression was initially down-regulated in the intestine during exposure to the low salinity stress. However, there was a significant increase in expression in the coelomic fluid at 48 h. The expression of Hsp70 mRNA peaked after 48 h in both coelomic fluid and respiratory tree and after 12 h in intestinal tissue. Quantitative analysis of the expression of these genes revealed significant differences among the different tissues and different exposure times. The expression profiles suggested that the four genes can be used as indicators of salinity stress. Given the changes in expression, the protein products of the four genes are likely involved in the regulation of metabolism as function proteins, or control the expression and the activity of the stress proteins as regulatory proteins, to improve the salinity stress tolerance of A. japonicus. Our results provide a foundation for studying the mechanism adaption of sea cucumber for the future study. Key words: Apostichopus japonicus; low salinity stress; glycine transporter; zinc finger protein; neuronal acetylcholine receptor; Hsp70