Abstract: Objective 　To investigate the effect of curcumin on express of regulation p300 and mechanism of anticancer in vitro. Methods 　The bladder T24 cell was treated with curcumin in different concentration. The cell growth inhibition was determined with MTT, the level of p300 、c-fos、c-jun mRNA were assayed by reverse t ranscriptase polymerase chain reaction (RT-PCR), and the expression of acetyl histone H3 and H4 、p300 、c-fos、c-jun protein were evaluated by western blot . Results 　Curcumin could significantly inhibit proliferation of T24 cell in a dose and time-dependent manner. The expression of p300 、c-fos、c-jun mRNA and protein was totally decreased with increasing concent rations of curcumin. Curcumin can inhibit the expression of acetyl histone H3 and H4 protein in a dose-dependent manner. Conclusion 　Curcumin can inhibit the expression of p300, which may be it s molecular mechanism of anticancer.