Abstract: Objective To investigate the expression of miR-122 in hepatocellular carcinoma cells and its relationship with cell cycle regulation. Methods The in situ hybridization and quantitative reverse transcription —PCR（qRT-PCR） were used to detect the expression of miR-122 in 50 cases of primary hepatocellular carcinoma and corresponding adjacent normal tissues，and flow cytometry was used to detect the cell cycle. The correlation between the expression of miR122 and the cell cycle was analyzed. Results The expression of miR122 in hepatocellular carcinoma tissues was（17.74±9.20）％ of adjacent normal tissues，while it was（19.89±8.80）％ in well and moderately differentiated hepatocellular carcinoma and（9.16±4.77）％ in poorly differentiated hepatocellular carcinoma； The positive rate of miR122 was 80.0％（40／50） in adjacent normal tissues， and 30.0％（15／50） in hepatocellular carcinoma（P＜0.05）. The percentage of S-phase cells was increased and the percentage of G1／G0 phase cells was decreased in hepatocellular carcinoma compared with the adjacent normal tissues （P＜0.05）. In the miR-122 negative expressed hepatocellular carcinoma， the percentage of S phase cells was increased and the percentage of G1／G0 phase cells was significantly decreased（P＜0.05）， compared with the miR-122 positive expressed hepatocellular carcinoma.Conclusion Downregulation of miR122 in hepatocellular carcinoma provokes the division and proliferation of cancer cells.