In this study,the inhibitory effect and mechanism of baicalein on tumor growth and lung metastasis of human breast cancer cell line MDA-MB-231 in nude mice was investigated.Twenty female BALB/C nude mice were randomly divided into normal group,model group,paclitaxel group and baicalein group.There were 5 nude mice in each group.The nude mice model of human breast cancer xenograft was established.Baicalein group was injected with 50 mg/kg baicalein abdominal cavity,paclitaxel group was injected with 10 mg/kg paclitaxel,normal group and model group were injected with normal saline for 8 weeks.Experimental results indicated that the tumor weight and the number of lung metastasis nodule and metastasis focus in paclitaxel group and baicalein group were less than those in the model group.Baicalein alone or in combination with ROCK inhibitor Y-27632 could inhibit the migration and cytoskeleton protein expression of MDA-MB-231 cells,reduce the formation of protein bundles,and inhibit the protein levels of ROCK1,Rac1,RhoA and p-MLC.