Objective To discuss the effect of Balint groups on promoting mental health of oncology nurses through developing Balint group activities. Methods From December 2015 to December 2016, a series of Balint group activities were carried out among 63 oncology nurses in West China Hospital of Sichuan University. Huaxi Emotion Index was used to investigate the psychological status in the nurses before and after the activities of Balint groups, and then the data was analyzed statistically. Result Except the scores of nurses aged over 41 and nurses above the primary and secondary level (P>0.05), all other scores had significant differences (P<0.05). Conclusions Balint group activities can significantly relieve oncology nurses’ negative emotions such as anxiety, tension and depression, alleviate body discomfort symptoms and improve interpersonal relationships. Huaxi Emotion Index is easy to understand, which helps rapid clinical assessment and nurses’ psychological problems screening. It is suitable for popularization and application clinically.