The adipocyte development process of C3H10T1/2 pluripotent stem cells includes two stages: the commitment stage and the differentiation stage．There are evidences that BMP4 commits C3H10T1/2 cells into preadipocytes．Previous studies have shown that mice lacking adipocyte Lrp1(adLrp1-/-) displays reduced body weight and smaller fat stores which highlights the important role of Lrp1 in adipogenesis．However, little is known about the role of Lrp1 in preadipocyte commitment．RNAi was used to study the effect of low density lipoprotein receptor-related protein 1(Lrp1) on commitment of C3H10T1/2 to preadipocyte．Through microscopic examination, Oil red O staining, Western blotting, it is demonstrated that Lrp1 RNAi inhibits C3H10T1/2 adipogenesis in commitment stage, rather than in lipid maturation period．BMP4 signals through Smad1/5/8 and Lrp1 RNAi significantly suppresses the BMP4-triggered phosphorylation of Smad1/5/8．These data suggest that Lrp1 RNAi has inhibitory effects on the BMP4-induced of C3H10T1/2 preadipocyte commitment via down-regulating Smad signaling.