Abstract: Objective 　To study the relationship between Cisplatin (CDDP) and radiation used in combination in human laryngeal squamous cells ( Hep-2), in order to determine the optimum sequence of the two treatment s, and the relations with telomerase activity. Methods 　Hep-2 cells were exposed to CDDP and ⁶⁰ Co gamma2irradiation with different dose and sepuence. Our group cells as follows : unt reated group 、CDDP group 、irradiation group 、CDDP + irradiation group and irradiation + CDDP group. MTT assay、PCR based Telomeric Repeat Amplification Protocol ( TRAP) coupled with EL ISA and polyacrylamide gelelect rophoresis ( PAGE) with sliver staining were used to estimate the cell survival rate and the telomerase activity ( TA) before and af ter t reatment s. Results 　The cell survival rate of the group t reated by CDDP plus radiation was lower than that by irradiation plus CDDP with significant statistical difference. Analysis of telomerase activity indicated that both CDDP and irradiation could independently increase telomerase activity in a dose dependent manner, however, addition of the other t reatment decreased TA, decreased range scale was consistent with change of cell survival rate. Conclusion 　The treatment of Hep-2 cell by chemotherapy plus irradiation is superior to that t reatment by irradiation plus chemotherapy : after combined t reatment s, TA can reflect the effect s of therapies.