Objective To investigate the mechanism of minoxidil’s promoting effect on cultured adult hair follicles. Methods Different concentrations of minoxidil was added on adult hair follicles cultured in serumfree medium. Hair growth was measured at different time points. The amount of collagen I, metalloproteinases1(MMP-1), transforming growth factor β1(TGF β1), integrin β1 and K19 were tested by histochemistry and immunohistochemistry. Results Cultured hair follicles grew fast during the first three days, and then grew slow afterwards. 1mg/L of minoxidil increased the growth of hair follicles most effectively among the concentrations from 0.1mg/L to 100mg/L. The appearance of catagen appeared later in minoxidil group than control. The expression of collagen I was stronger in minoxidil group than in control; the expression of MMP-1 and TGFβ1 were less. There was no significant difference of the expression of integrin β1 and K19 between experiment and control groups.Conclusion Minoxidil can promote the g