Background: A variety of life event scales have been developed by the academic community in an attempt to detect and assess the direct and indirect impacts of negative life events on individual mental health. Despite their significant role in clinical medicine and psychological counseling, deficiencies remain in both theoretical and empirical aspects. Objective:The aim of this study is to develop and validate a self-rating scale for the severity of negative life events, based on the theoretical perspective of phenomenological psychopathology, with a focus on the subjective negative experiences of patients with depression. Methods: A sample of 123 patients with depression completed the Self-Rating Scale for the Severity of Negative Life Events(NLESS), the Beck Depression Inventory (BDI), the 9-item Patient Health Questionnaire (PHQ-9), the Psychological Distress Thermometer (PDT), and the Social Readjustment Rating Scale (SRRS). Conclusion: Developed on the theory of phenomenological psychopathology and centered on subjective negative experiences as its core content, the self-rating scale for the severity of negative life events exhibits good psychometric properties and holds promising application prospects in clinical practice.