Aim To investigate the effect of Alisma Decoction on expressions of cyclin D1, cyclin E, proliferating cell nuclear antigen (PCNA) and p27 in vascular smooth muscle cell (VSMC), and to explore the effect and mechanism of Alisma Decoction in VSMC proliferation induced by oxidized low density lipoprotein (ox-LDL). Methods The atherosclerosis cell model of VSMC proliferation was established through induction of VSMC by 50 mg/L ox-LDL in vitro, and was intervened with normal rat serum (blank serum) and 20% Alisma Decoction-containing serum. The effect of Alisma Decoction-containing serum on VSMC proliferation was detected by MTS method. Expressions of proliferation associated proteins such as cyclin D1, cyclin E, PCNA and p27 were determined by Western blot. Results 50 mg/L ox-LDL could obviously promote VSMC proliferation. Compared with the ox-LDL group, Alisma Decoction-containing serum significantly inhibited VSMC proliferation induced by ox-LDL. Investigation demonstrated that Alisma Decoction-containing serum could decrease the expression level of cyclin D1, cyclin E and PCNA, at the same time, increase the expression level of p27. Conclusion Alisma Decoction can inhibit ox-LDL-induced VSMC proliferation, and its mechanism may be related to increasing p27 expression and inhibiting cyclin D1, cyclin E and PCNA expression.