Epigenetic regulation of the related genes DNA methyltransferase (DNMT1), histone deacetylase (HDAC3), and histone methyltransferase (MLL5) were used to analyze gene-expression quantity in the respiratory tree, intestine, coelomic fluid, and muscle tissue of the sea cucumber under high-temperature stress conditions. The housekeeping gene of the sea cucumber was used for internal calibration, and the relative quantification 2^{-ΔΔmethod was employed using real-time fluorescent quantitative PCR. Sea cu­­cumber kept at <15℃ were used as a control group, and the target gene-expression quantity of this group was used as benchmark-1. Increased expression of the DNMT1 gene was insignificant in the coelomic fluids at 18℃, but the expression rose significantly between 18℃ and 21℃, thereafter the increase was less acute, until the ex­pres­sion quantity reached a maximum of 3.26 at 30℃. The expression quantity of the MLL5 gene and the HDAC3 gene were significant at 2℃, and then the expression quantity increased slightly as the temperature increased, reaching a maximum of 2.90 and 3.19, respectively, at 30℃. Overall, the expression quantity of the three genes increased with increasing temperatures, and this trend was obvious, reaching a maximum at 30℃. Comparisons of different tissues showed diverse expression quantities of the three genes. Expression of the genes was prominent in the coelomic fluids, at >2.5, above 24℃, while the expression quantity of the three genes in muscle tissue was <2 in the whole spectrum of high temperatures. Under the stress conditions of 30℃, the gene-expression quantity of the three genes was detected at 0 h, 3 h, 6 h, 9 h, 12 h and 15 h, and the expression quantity of every gene at 0 h was used as benchmark-1. The data showed that the expression quantities of the three genes were characterized by increasing expression with the extension of stress time during 0 to 9 h (<0.05), except expression of HDAC3 in intestine stabilized at about 6 h. The expression quantity was either not obviously or only slightly lower after 9 h. In addition, the trend in expression quantity was consistent in the different tissues, yet the maximum expression quantity of every gene was highest in the coelomic fluids than in any of the other tissues. This expression analysis of epigenetic-related genes under high temperatures lays a foundation for interpreting the mechanism of response to high-temperature stress in sea cucumber from the viewpoint of epigenetic regulation.}