Objective To explore nurses' dispositional optimism and mental health and disscuss the impact of dispositional optimism on nurses' mental health in order to provide evidences for promoting the level of nurses' mental health. Methods Adopting Revised Life Orientation Test (LOT-R) and Symptom Checklist 90 (SCL-90) ,the researchers carried on the questionaire investigation to a total of 240 nurses. Results Unmarried nurses were more optimistic than married ones(15.53 ± 3.48,14.39 ± 2.88) ,and the difference had statistic significance(P ＜ 0.01). The positive detection rate of nurses' psychological symptoms was 6.7% ～ 26.5%. Compulsion, interpersonal sensitivity and depression were nurses' main psychological symptoms. Compared to the national female norm, the somatization, depression, anxiety, psychosis factor scores, total score and the number of positive items of SCL-90(1.49±0.45,1.70±0.42, 1.55 ±0.43,1.46±0.38,1.40±0.37,1.50±0.35,37.23±22.02)were higher, and the difference had statistic significance(P＜ 0.05). Dispositional optimism postively correlated with the level of nurses' mental health(P＜ 0. 001). Conclusions The general condition of nurses' mental health is not good enough, and dispositional optimism has good forecast function to nurse's mental healthy. Therefore, maintaining positive and optimistic attitude will be helpful to nurses' mental health.