Aim To investigate the effect and the possible mechanism of homocysteine （Hcy） on vascular smooth muscle cells （VSMC） calcification.Methods VSMC were treated with Hcy,endoplasmic reticulum stress （ERS） inhibitors 4-Phenylbutyric acid （PBA） and taurine （TAU）. Alizarin red staining,calcium content and alkaline phosphatase （ALP） activity assay were used to determine VSMC calcification. Western Blot was used to measure the protein expression of endoplasmic reticulum stress （ERS） markers.Results Hcy with different concentration （50,100,200,400 μmol/L） can exacerbate VSMC calcification. Compared with the calcification group,calcium content of VSMC was increased by 2.5-fold （P<0.01）,4.17-fold （P<0.01）,5.83-fold （P<0.05） and 8.33-fold （P<0.01） respectively,the ALP activity,was elevated by 1.56-fold （P<0.05）,2.18-fold （P<0.05）,2.56-fold （P<0.01）,and 3.13-fold （P<0.01）,respectively. Hcy could increase expression of ERS markers,p-PERK,p-IRE1,and ATF6 were increased by 37.8%,27.5%,and 26% （All P<0.05） respectively,compared with calcification group alone. PBA and TAU inhibited the increase in ERS related proteins which induced by Hcy,compared with Hcy group,p-PERK decreased 64% and 76% （both P<0.01）,p-IRE1 decreased 65% and 41.1% （both P<0.01）,ATF6 decreased 50% and 47% （both P<0.01）,CHOP decreased 47.4% and 39.5% （both P<0.01）,PERK decreased 58.6% and 69% （both P<0.01）,GRP78 decreased 79.5% and 72.7% （both P<0.01） treated with PBA and TAU. ERS inhibitor PBA and TAU could inhibit VSMC calcification induced by Hcy,calcification node,ALP activity and calcium content were reduced by PBA and TAU. In addition,PBA and TAU also blocked the VSMC contractile phenotype transforming into to osteoblast-like phenotype induced by Hcy. Compared with Hcy group,SMα-actin increased by 2.9-fold and 3.1-fold （both P<0.01）,SM22α increased by 1.8-fold and 2.3-fold （both P<0.01）,OPN decreased by 2.73-fold and 4.2-fold （both P<0.01） by PBA and TAU respectively.