Objective To observe the application of 3.0T MRI in the diagnosis of triple negative breast cancer and provide a reference for preoperative clinical diagnosis. Methods 110 cases of women with breast cancer admitted to our hospital from March 2015 to March 2018 were given retrospective analysis. According to the pathological examination results, patients were divided into triple negative breast cancer group (TNBC group, 42 cases) and non-triple negative breast cancer group (non-TNBC group, 68 cases). 3.0T magnetic resonance imaging diffusion-weighted imaging (MRI-DWI) was used for breast scan, and the pathological features (tumor number, size, shape, smooth edges or not, number of peripheral blood vessels, etc.) were compared between the two groups, and the MRI dynamic enhancement characteristics were observed in the two groups, and the time-signal intensity curve (TIC) types, T2WI signal intensity and ADC value were compared between the two groups. Results Compared with non-TNBC group, tumors were mostly round with smooth edges and increased peripheral blood vessels in TNBC group (P<0.05). The MRI dynamic enhancement was mainly based on annular enhancement in TNBC group while was mainly based on uneven enhancement in nonTNBC group (P<0.05). There was no significant difference in the TIC curve types between the two groups (P>0.05), but TNBC group was mostly with streamline type, and non-TNBC group was mostly with efflux and plateau types. The lesions in TNBC group were mostly high signal in T2WI with low ADC value, and the lesions in non-TNBC group were mostly low signal with slightly high ADC value (P<0.05). Conclusion 3.0T MRI technique can be used to observe the morphological characteristics of tumors in non-invasive conditions, and it is helpful for the identification of malignant tumors such as triple negative breast cancer, and provides reference for later clinical treatment regimen.