Aim To observe the effect of flavonoids from Astragalus complanatus(ACF) on the growth of SMMC7721 human liver caner subcutaneous transplanting tumor in nude mice. Methods After the nude mice model of the subcutaneous transplanting tumor was established by human liver cancer SMMC7721, 30 cases were randomly divided into model group, CTX group,ACF-1 group,ACF-2 group and ACF-3 group(n=6,each),treated with saline, CTX and ACF respectively.The expression level of proliferation cell nuclear antigen (PCNA) in the tumor tissues was also investigated by immunohistochemical methods. The histopathological changes were observed by light microscopy and electromicroscopy. Results In comparison with that in the model group, the size and weight of tumors in ACF group were significantly decreased. The expression level of PCNA in tumors was decreased in both ACF-1 group and ACF-2 group, comparing with the control(P