Abstract: Objective: To investigate the dynamic changes of psychological distress in breast cancer patients after diagnosis, and determine the related factors of psychological distress. Methods: A longitudinal study design was used to evaluate the psychological distress, social support, and coping style at the time of diagnosis, and 1, 3, 6 months after diagnosis, to compared the difference and analyze the related factors of psychological distress. Results: The incidence of moderate or high psychological distress in patients with breast cancer was 63.9% (T1), 78.2% (T2), 69.4% (T3), and 33.3% (T4), and the mean score was 4.08±1.59 (T1), 4.66±1.47 (T2), 4.40±1.99 (T3), 2.89±1.60 (T4), respectively. The related factors of psychological distress included time of diagnosis, age, education level, economic status, family history, social support and coping style. Conclusion: The psychological distress is popular in breast cancer patients, and the psychological distress level is dynamic. Psychological intervention should be strengthened to improve the patients' psychosocial status.