Objective:To measure parameters of survival curves of a pulmonary adenocarcinoma cell line SPCA-1 in vitro.M ethods:Two groups were studied in this experiment, which included irradiation alone and combination of irradiation with mild hyperthermia.The former was given single high photon irradiation with 6M X-ray 2, 4, 6, 8街respectively. Hyperthermia was applied to the latter,41.5 degrees Centi grade, 1 h, after having received same irradiation. The cel surviving fractions were determined by clonogenic assay and the parameters of the multi-target/single-hit model, Do, D9, as well as those of the linear-quadratic model, ratio of alpha and beta, were elicited. Results: The parameters of the irradiation combining with hyperthermia, Do and Dq, were 1.390 and 1.426 Gy,whereas they were 1.693 and 2.453 Gy for irradiation alone, respectively. The surviving fraction at 2 Gy(SFZ) was 0.793 versus 0.532 of the combination. The ratio of alpha and beta increased from 0.992 to 7.725 Gy and the SFZ of the linear-quadratic model decreased from 0.743 to 0.459. Conclusion: The values of Do and SFZ show that the radiosensitivity is low relatively, though mild hyperthermia might induce radiosensitization of SPC-A-1 cells.