Objective To explore the clinical value of quantitative dynamic contrastenhanced magnetic resonance imaging (DCE-MRI) region of interest (ROI) delineation in the diagnosis of breast cancer. Methods 57 female patientsexamined by DCE-MRI in the hospital from January 2015 to June 2017 were selected, and ROI delineation was performed. The volume transfer constant (Ktrans), reflux velocity constant (Kep) and extravascular space volume (Ve) were measured. The above parameters were compared among breast cancer, benign breast lesions and normal glands. The diagnostic efficiencies of different quantitative parameters for breast properties were analyzed by ROC curve. Results There were statistically significant differences of Ktrans, Kep and Ve among the three groups (P<0.05). The Ktrans and Kep showed the breast cancer group > the benign lesion group > the normal gland group (P<0.05), while Ve showed the breast cancer group < the benign lesion group < the normal gland group (P<0.05). The areas under ROC curve of Ktrans, Kep and Ve in the diagnosis of benign and malignant breast lesions were 0.802, 0.915 and 0.736 respectively, the sensitivities were 92.26%, 92.34% and 83.17% respectively, and the specificities were 58.25%, 74.68% and 66.62%, respectively. The area under ROC curve of Ktrans combined with Kep was 0.941, the sensitivity and specificity were 97.33% and 83.49% respectively. Conclusion The quantitative parameters of DCE-MRI, Ktrans, Kep and Ve are of great value in the diagnosis of benign and malignant breast lesions. Besides, Ktrans combined with Kep can improve the diagnostic efficiency.