OBJECTIVE To observe the effects of watersoluble minoxidil(WMD) on hair growth and hair cycle of C57BL/6 mouse alopecia model.METHODS Anagen was induced over the back of telogen mice by depilation of hair shafts with wax∶resin(1∶1) mixture.The experimental mice were treated tropically once daily using respectively 1% WMD,1.5%WMD and 3% WMD for 21 days,meanwhile the daily changes of skin color and the score of the final hair growth characteristic were observed.Furthermore,the effects of WMD on hair growth were evaluated by measuring hair weight and length,dermis thickness and the number of follicle in mice.RESULTS The skin color of experimental mice turned from pink to black is 24h earlier than that of control mice,and gray from black delay 48h compared with that of the latter.Moreover,it was remarkable difference in statistics of hair length,dermis thickness and the number of follicle except hair weight in experimental mice compared with model mice,and it was expecially obvious in 1.5%WMD group.CONCLUSION WMD not only can induce and prolong anagen,but also postpone catagen in C57BL/6 mice.Moreover,WMD can promote hair growth of experimental mice.