Abstract: Monopterus albus is sex reversal, this study aims to find sequence sites directly related to sex regulation, and analyze sequence differences in male and female Monopterus albus. In this experiment, the Dmrt3 gene was taken as the research object, by comparing the gene methylation status in male and female gonads, specific sites of sex control were analyzed. Using methylation sensitive restriction enzyme Hpa II, the DNA of Monopterus albus’s gonad was cut and the enzyme digested products were amplified by each primer according to the known mRNA sequence. At the same time, the control group with no enzyme was compared with the test group, to analyze the different bands and to verify the results. The experimental results showed that Dmrt3-FR2 amplification sequences had no methylation sites in the testis, but had methylation sites in ovarian. Therefore, we speculate the site may be related to sex regulation. This experiment is a supplement to the study of sex control from the molecular angle in Monopterus albus, and proves the feasibility of using methylation to research sex control, it may provide a theoretical basis for the other researches.