In this paper, the changes of telomerase activity in human liver cells after exposed to the heavy ion radiation were investigated. Irradiation was performed at the Heavy Ion Research Facility in Lanzhou (HIRFL). The hepatocellular cells HL-7702 and the hepatocellular carcinoma cells SMMC-7721used as model cell were exposed to ,12,C,6+, irradiation at 0, 1, 2, 3 and 4Gy and formal irradiated cell was re-cultured for 72h and later irradiated cell was re-cultured for 24h and 72h respectively. PCR based on telomeric repeat amplification protocol (TRAP-PCR) method was used to determine the telomerase activity in SMMC-7721 and HL-7702, respectively. It has been found that the HL-7702 cells don’t express the telomerase activity at 0Gy, 1Gy and 4Gy while the cells exposed to 2Gy and 3Gy express the telomerase activity clearly (,p,<,0.05). But when the SMMC-7721 cells are exposed to heavy ionizing radiation at 1~3Gy, the telomerase activity significantly increases in a dose and time dependent manner (,p,<,0.05). From this experimental results it can be concluded that heavy ionizing radiation, as a high LET radiation, could induce changes of telomerase activity. It can also be indicated that telomerase participates in the repair process of DNA exposed by heavy ionizing radiation and ,12,C,6+, in tumor therapy could kill tumor cells more efficiently than that by the other low LET rays.