In the paper the human hepatoma cells SMMC-7721 were irradiated by 80 MeV/u ^20Ne^10+; phase changes of irradiated cell cycle were detected by Flow Cytornetry (FCM) within 24 h. The purpose is that the relationships between phase changes of cell cycle induced by heavy ions and dose, repair time are found so as to accumulate necessary basic data for clinical application of cancer therapy with heavy ions.