The incidence of brain metastasis of Her2-negative breast cancer is high, which seriously affects the prognosis of patients.The treatment of brain metastasis of Her2-negative breast cancer is still tricky. The local efficacy of head radiotherapy for breast cancer brain metastases is remarkable, and systemic tumor progression in patients with brain metastases is the main reason for treatment failure. Sacituzumab Govitecan is the only Trop-2 antibody-coupled drug (ADC) approved for the treatment of unresectable locally advanced or metastatic Her2-negative breast cancer. However, the objective remission rate of Sacituzumab Govitecan for intracranial metastatic lesions has not been satisfactory. This study is an open, uncontrolled phase II clinical study to observe the efficacy and safety of Sacituzumab Govitecan combined with intracranial radiotherapy in the treatment of patients with brain metastases from Her2-negative breast cancer, in order to find a more effective treatment method.