Aim To investigate the differentiation of marrow stromal cells induced by low density lipoprotein(LDL) into smooth muscle-like cells and the role of myocardin in it. Methods Bone marrow stromal cells(BMSC) of mouse were purified by disparation adherence technique.The cultured BMSC were divided into 4 groups: regular culture group,regular culture+LDL group(LDL 25 mg/L),20% fetal bovine serum(FBS) culture group,20% FBS culture+LDL group.The expression of myocardin,α-SMA and SM-MHC were detected by immunocytochemistry technique.RT-PCR was used to detect the mRNA expression of myocardin,α-SMA and SM-22α. Results It is showed by immunocytochemistry that the expression of myocardin,α-SMA and SM-MHC expressed in regular culture+LDL group(LDL 25 mg/L),20% fetal bovine serum(FBS) culture group,20% FBS culture+LDL groups were signifcnatly higher than that in regular culture group(P<0.05).The expression of the three proteins in 20% FBS culture+LDL group were significantly higher than that in 20% fetal bovine serum(FBS)group(P<0.05).The proteins expression of α-SMA(r=0.9018,P<0.05) and SM-MHC(r=0.7969,P<0.05) were positively related with myocardin.It is approved by RT-PCR that the mRNA expression of myocardin,α-SMA and SM-22α in regular culture+LDL group(LDL 25 mg/L) 20% fetal bovine serum(FBS),20% FBS culture+LDL group.groups were significantly higher than that in regular culture group(P<0.05).The mRNA expression of the three genes in 20% FBS culture+LDL group were significantly higher than that in 20% fetal bovine serum(FBS) group(P<0.05).The mRNA expression of α-SMA(r=0.9295, P<0.05) and SM-22α(r=0.8940,P<0.05) were positively related with myocardin. Conclusion Both 20% FBS and LDL could induce the differentiation of BMSC into smooth muscle-like cells.The role of LDL with 20% FBS inducing the differentiation of BMSC into smooth muscle-like cells was the strongest.And myocardin may play an important role in this differentiated process.