Abstract: Objective To investigate the radiosensitizing effect and underlying mechanism of hyperthermia on human esophageal carcinoma cell line EC-1. Methods The radiosensitizing effect of hyperthermia human on esophageal carcinoma cell line EC-1 by fi tting the dose-survival curving‘multitarget click mathematical model'.Flow cytometry (FCM) was used to detect the changes of cell apoptosis and cell cycle．Results Hyperthermia had an obvious radiosensitization on human esophageal carcinoma EC-1 cells. After treatment with hyperthermia for 30 minutes, the sensitization enhancement ratio was 1.060，the G2/M phase ratio increased while S phase and G₀/G₁ phase decreased. The apoptosis ratio increased significantly(P0.05). Conclusion Hyperthermia can enhance the radiosensitivity, and combination of them could enhance it more signifi cantly. Hyperthermia can enhance the killing effect of radiation on tumour cells mainly through affecting the EC-l cell cycle, and the induction of apoptosis is the second reason.