Objective: To explore reciprocal action between BMP 2 (bone morphogenetic protein 2) and BMP 3 for better understanding of the mechanism of BMP during bone fracture union. Methods: rhBMP 2 was added into the cultured fibroblasts with the concentration of 1 200 ng/ml. The expression of BMP 3 in fibroblasts was detected by immunohistochemistry. Eukaryotic expression vector pcDNA3 BMP 3 was transfected into the fibroblasts. After the effective expression of BMP 3 was identified, BMP 2 was also detected by immunohistochemistry in BMP 3 expression cells. The fibroblasts transfected with empty vector pcDNA3 were used as the control. Results: Exogenous rhBMP 2 could promote the expression of BMP 3 in fibroblasts. BMP 3 also could be detected in these cells.Conclusions: BMP 2 and BMP 3 could reciprocally adjust the expression in fibroblasts. Objective: To explore reciprocal action between BMP 2 (bone morphogenetic protein 2) and BMP 3 for better understanding of the mechanism of BMP during bone fracture union. Methods: rhBMP 2 was added into the cultured fibroblasts with the concentration of 1 200 ng / ml . The expression of BMP 3 in fibroblasts was detected by immunohistochemistry. Eukaryotic expression vector pcDNA3 BMP 3 was transfected into the fibroblasts. After the effective expression of BMP 3 was identified, BMP 2 was also detected by immunohistochemistry in BMP 3 expression cells. The fibroblasts transfected with empty vector pcDNA3 were used as the control. Results: Exogenous rhBMP 2 could promote the expression of BMP 3 in fibroblasts. BMP 3 could could be detected in these cells. Conclusions: BMP 2 and BMP 3 could reciprocally adjust the expression in fibroblasts .