Abstract: Objective To investigate the influencing factors of mental health of breast cancer patients undergoing radiotherapy after breast-conserving surgery. 
Methods A total of 120 patients with breast cancer undergoing breast-conserving surgery were selected as the research subjects. All patients received radiotherapy after operation. The patients were investigated with Eysenck Personality Questionnaire(EPQ) before and after radiotherapy, and the changes of mental health status before and after radiotherapy were evaluated. Univariate and multivariate Logistic regression models were used to analyze the factors influencing the mental health status of patients after radiotherapy. 
Results The scores of P scale, N scale and L scale after radiotherapy were significantly lower than those before radiotherapy, while the score of E scale was significantly higher than that before radiotherapy, with significant difference(P＜0.001). P scale, E scale, N scale and L scale were used as dependent variables, and multivariate regression analysis was performed. It was shown that marital status, economic income, religious belief, tumor stage, tumor size, lymph node metastasis and family history were factors affecting the mental health of breast cancer patients after breast-conserving surgery. 
Conclusion Radiotherapy after breast-conserving surgery can help improve the mental health of patients with breast cancer. Marital status, economic income, religious belief, tumor stage, tumor size, lymph node metastasis and family history are the influencing factors of mental health status of breast cancer patients undergoing radiotherapy after breast-conserving surgery. 

Key words: breast neoplasms, radiotherapy, influencing factor analysis