Abstract: Breast cancer is the most frequent female malignant tumor. BRCA1 and BRCA2 genes are important susceptibility genes of breast cancer. Mutations in BRCA1/2 genes lead to an increased risk of breast cancer in life-span. The most common mutations in BRCA1/2 genes are frameshift and nonsense mutations involving in one or several bases by Sanger-sequencing. However, large rearrangements of BRCA1/2 genes are hardly detected by conventional Sanger-sequencing. With the progress of gene detection technology, multiple BRCA1/2 gene rearrangements have been found, we need to take the large rearrangement into consideration when no mutation is found in traditional BRCA1/2 gene sequencing on the family of hereditary breast cancer, in order to avoid missed diagnosis.