Objective To explore the effect of nandrolone phenylpropionate (NP) on rats’ fibroblasts after injury. Methods After being isolated from granulation tissue of a onemonth wistar rat,the fibroblasts(FB) were grouped into 5 groups and cultured in RPMI1640 and 5%FBS culturing liquid with 0.5,1.0,5.0,10.0,and 15.0 μg/ml NP respectively. The control group was cultured in RPMI1640 and 5% FBS culturing liquid Fibroblasts were isolated from granulation tissue of a onemonth Wistar rat and cultured with RPMI1640 culturing liquid with 5% FBS added different doses of NP from 0.5～15.0 μg/ml in NPgroup, but only 5% FBS for the control group. Cell validity of fibroblasts was measured by MTT. The proliferetive index(PI) of the most effected group was measured by flow cytometry. Results Compared with control group, higher FB validity occured in every NP group (P＜0.05) The PI of FB in every NP group measured by flow cytometry was significantly higher than that in controlgroup(Plt;0.01). Conclusion NP can promote the replication and proliferation of FB.