Objective:To investigate the effect of FCCP on differentiation of P19 cells to cardiomyocytes. Methods:P19 cells were treated with 5 umol/L FCCP and untreated cells were used as controls,the morphologic changes of P19 cells at indicated time during the differentiation were observed and photographed under an inverted microscope. The expressions of GATA4,NKX2.5 and cTnT were detected using Real-time PCR and Western blot in the differentiated process. Results:Compared to the control group,the embryoid bodies formed in the FCCP treated group were smaller and were loosely structured. The expressions of GATA4,NKX2.5 and cTnT were observed in the two groups,while FCCP treated cells present with a slower dynamic changes during the differentiation. Western blotting results showed that the protein expressions of GATA4,NKX2.5 in the FCCP treated group on day 5,7 and 9 were lower than that of the control group,respectively. For the expression of GATA4 protein on day 11,there was no significant difference between the two groups,while the expression of NKX2.5 protein in the FCCP treated group was lower compared with the control group. The protein expressions of cTnT on day 5,7 showed no significant difference within the two groups,and with further differentiation,the expression of cTnT protein in the FCCP treated group increased but was still lower than the control group on day 9,11,respectively. Conclusion:FCCP inhibited the differentiation of P19 cells to cardiac myocytes.