In order to study the effect of UHRF1 on growth and radiosensitivity of breast cancer MDA-MB-231 cells, The stable clones of MAD-MB-231 cells with UHRF1 gene overexpression were established by transfection of a full-length human UHRF1 cDNA which was cloned into a mammalian expression vector pcDNA3. And the effect of UHRF1 on growth of MDA-MB-231 cells was identified by population double time and colony formation assays. The change of radiosensitivity after γ-irradiation was determined by colony formation assay. It has been found that enhanced expression of UHRF1 does not affect cell growth and colony formation. However, in comparison with MAD-MB-231 parental cells and MAD-MB-231/pcDNA3 cells, MAD-MB-231/UHRF1 cells are less susceptibility to γ-irradiation. These results indicate, for the first time, that human UHRF1 may be an important mediator in radiotherapy of breast cancer, although further study is still needed.