Objective To deeply understand the psychological experience of non-suicidal self-injury in adolescent mental disorder patients during hospitalization, so as to provide reference for developing targeted nursing intervention. Methods Eighteen adolescents with mental disorders who conducted non-suicidal self-injury (NSSI) during hospitalization were selected using purposive sampling method, then semi-structured interview was conducted with them to collect data. The topic was extracted using Colaizzi′s 7-step analysis method. Results Four themes were identified, namely, unmanageable negative emotions, controlled by symptoms, self-ambivalence, and lack of motivation for seeking help. Conclusion Nursing staff should pay attention to the psychological feelings of adolescent mental disorder patients with non-suicidal self-injury and their emotion changes, strengthen social support, and provide personalized psychological nursing, so as to prevent non-suicidal self-injury and ensure the safety of patients.