The cDNA sequence of HpGST gene was cloned，and bioinformatics analysis and expression analysis of it were carried out to study the function of glutathione S-transferase gene （HpGST） in Hylocereus.The results showed that the cDNA sequence of HpGST was 666 bp in length，encoding 221 amino acids.The encoded protein belonged to non-secretory unstable hydrophilic protein，and its subcellular localization predicted its role in the cytoplasm.The phylogenetic tree shows that it is closely related to Chenopodium quinoa，and belongs to the Tau family of glutathione transferases.The results of real-time fluorescent quantitative PCR analysis showed that HpGST was expressed in the flesh of different color types of Hylocereuss.The expression levels of HpGST in purple and pink flesh of Hylocereuss with pigment accumulation were significantly higher than those in white flesh types without pigment accumulation.The expression trend was first increased and then decreased with the development of fruit.Its expression level was positively correlated with content of betaine，and the expression trend in different varieties is highly consistent with the accumulation trend of betaine.It is indicated that HpGST gene plays an important role in the synthesis and distribution of betaine in Hylocereus.