Objective To observe the effect of GPR30 agonist G1 on high glucose-induced endoplasmic reticulum stress (ERS) in endothelial EA.hy926 cells. Methods EA.hy926 endothelial cells were divided into three groups: normal control group (Con, 17.51 mmol/L glucose), high glucose (HG, 33.3 mmol/L), high glucose +G1 group (HG +G1, HG +1 μmol/L G1). The apoptosis rate of endothelial cells was measured by flow cytometry, the protein expression changes of ERS related molecules Bip, IRE1, PERK and apoptotic molecules Bax, Bcl-2 were measured by Western blot, the mRNA expressions of Bip and CHOP were measured by RT-PCR assay. Results Compared with Con group, the apoptosis in HG group was significantly increased (P <0.01), Bip, IRE1, PERK and apoptotic molecule Bax were upregulateded (P<0.05, P<0.01 or P <0.001), Bcl-2 downregulatted (P <0.01) and Bip mRNA, CHOP mRNA expression were upregulated (P <0.001 and P<0.01). Compared with the HG group, apoptosis rate in HG +G1 group was significantly lower (P <0.05), BIP, IRE1, PERK and apoptotic molecules Ba.0 downregulated (P <0.05 or P <0.01), Bcl-2 expressions was increased (P <0.05), Bip mRNA and CHOP mRNA expression were decreased (P<0.001 or P<0.01). Conclusion GPR30 agonist G-1 inhibits EA.hy926 ERS in endothelial cells.