Background: X-ray chest fluoroscopy is a compulsory component of the health examination procedure in China. The radiation dose from chest fluoroscopy is the largest in X-ray examination. More than half of the women in their twenties with breast cancer have been given X-ray fluoroscopy. Studies have shown that Caveolin-1 is involved in the repair of damage DNA in tumor cells induced by irradiation. However the mechanism and role of Caveolin-1 in normal human mammary epithelial cells are not clear.  Materials and Methods: Here, normal human mammary epithelial cells (MCF10A) and the cells with Caveolin-1 knockdown (MCF10A^CE) were exposed to X-ray radiation to investigate the role of Caveolin-1 in the enhancement of radiosensitivity in these cells and the associated mechanism. Results: Decreased survival rate and a significantly higher level of cell arrest at the G1 and G2 phases, as well as reduced activation of the DNA damage repair proteins ATM and p53, and the stress protein p38MAPK were manifested by MCF10A^CE cells compared to MCF10A cells, following exposure to X-ray radiation. Furthermore, binding between Caveolin-1 and Mdm2 in MCF10A^CE cells was also lower than in MCF10A cells. Conclusion: Overall, the finding indicated that Caveolin-1 played an important role in decreasing the radiosensitivity of human mammary epithelial cells.