This study investigates the toxicity of CdTe quantum dots (QDs) on mouse ovarian granulosa cells in vitro. The fluorescence stabilities of QDs in DMEM culture medium, M1640 culture medium and phosphate buffer solution (PBS) are measured by fluorometer, respectively. Apoptosis is observed by chromatin staining with Hoechst32258 and cell viability is detected by cell counting kit-8 (CCK-8) assay after the granulosa cells are treated with QDs. The results demonstrate that the fluorescence stability of QDs in DMEM culture medium is better than that in the other media, the QDs fluorescence emission spectrum in it does not shift and the intensity decreases only 9.8%. It is found that the apoptosis of granulosa cells treated with QDs is dosage-dependent by the Hochest32258 staining, which is confirmed by the CCK-8 assay. The research demonstrates that the QDs at lower concentration have not affected the morphology and function of granulosa cells in vitro. However, with the increase of accumulation of QDs inside cytoplasm, the apoptosis increases significantly. This study offers very useful information of reproductive toxicity of QDs to guide the safe application of QDs in vivo.