Abstract: Objective: To determine the effects of ionizing radiation on the proliferation of keloid fibroblasts (KFb). Methods: The cllular morphology, viability, proliferation and cell cycle of KFb before and after ionizing radiation were detected by MTT and flow cytometry. The change of the collagen level before and after treatment was measured by detecting the level of the hydroxyproline in the supernatant of the co-culture. Results:The proliferation inhibition rate of KFb after 4Gy irradiation for 72 hours was (47.88±1.82)%  which was higher than that of normal skin fibroblast (39.86±0.07)%, (P<0.05). The cellular morphology of KFb was abnormal. The level of hydroxyproline was (11.749±0.9428) μg/mL and (18.689±0.8484)μg/mL before and after irradiation for 72 hours respectively (P<0.05). Conclusion: Ionizing radiation inhibits the proliferation of KFb and the generation of collagen

Key words: ionizing irradiation, keloid fibroblast, collagen