Objective To investigate the effect and mechanism of decitabine (DAC) on the proliferation of human cholangiocarcinoma CCLP1 cells in vitro and in vivo.Methods After treated with various concentrations of DAC,cell growth inhibition rates were determined by CCK-8 assay.Cell cycle and cell apoptosis were analyzed by flow cytometry.Cell autophagy was observed under fluorescence microscope.The effect of DAC on the growth of cholangiocarcinoma in vivo was determined in a CCLP1 mice xenograft model.Results The proliferation rate of CCLP1 cells in the DAC-treated group decreased in a time-concentrated dependent manner.After treatment with DAC,the cell cycle of CCLP1 cells was arrested at the G2/M phase.The apoptosis rate was significantly higher in the treatment group over the control group.Cell autophagy was observed after treatment with DAC in CCLP1 cells.The tumor growth of implanted CCLP1 cells significantly slowed down after the mice were treated with 0.8 mg/kg DAC,6 times weekly for 2 weeks.Conclusion DAC can inhibit the proliferation of cholangiocarcinoma in vitro and in vivo.