Objective To evaluate the impact of clinical and pathological factors on incidence and prognosis of brain metastasis from breast cancer.Methods The clinical data of 4473 stage Ⅳ breast cancer patients were collected from The Surveillance,Epidemiology,and End Results (SEER) database.All these patients were divided into brain metastasis group (n=345) and non-brain metastasis group (n=4 128).The clinical and pathological factors between the two groups were compared using x2 test and binary Logistic regression.The OS of 345 brain metastasis patients was calculated using the Kaplan-Meier method and impact of clinical and pathological factors on the survival rate was analyzed by Log-rank method.Multivariate Cox regression model was used to find out the independent risk factors.Results Between brain metastasis group and non-brain metastasis group,these following clinical and pathological factors showed the scatistical significance on brain metastasis:age,histological grade,T stage,N stage,ER,PR and HER expression (P＜0.05).Binary Logistic regression results showed that age,T stage,N stage,ER,PR were independent factors affecting brain metastasis (P＜0.05).The prognosis analysis showed that marital status,histological grade,ER,PR,molecular subtype,radiotherapy and chemotherapy,surgery at primary lesions,surgery at metastasis site,liver metastasis,lung metastasis and numbers of other organs metastasis were significantly correlated with the survival of breast cancer patients with brain metastasis (P＜0.05).Cox regression analysis showed that histological grade,ER,PR,molecular subtype,radiotherapy and chemotherapy,surgery at primary lesions,surgery at metastasis site were independent prognostic factors in breast cancer patients with liver metastasis.Conclusions Breast cancer patients with brain metastasis have a poor prognosis.Molecular subtype should be considered for prediction of prognosis for patients with brain metastasis.Radiotherapy and surgery at metastasis or primary site may improve survival of patients.