Objective: To explore the psychological connection between non-suicidal self injury (NSSI) behavior and childhood trauma among vocational college students, thereby informing the optimization of mental health services. Methods: From June to July 2025, 18 students with NSSI behavior and childhood trauma were recruited from two vocational colleges in Heze City for semi structured interviews. Data were analyzed using Colaizzi s seven step analysis method for coding and thematic extraction. Results: Four core themes and ten subthemes were identified. Childhood trauma drove NSSI behavior through four interrelated psychological pathways, containing a cognitive pathway for internalization of traumatic beliefs and self punishment, an emotional pathway for dysregulation of traumatic emotions and compensatory behaviors, a somatic behavioral pathway for somatization and reenactment of traumatic memories, and an interpersonal pathway for impaired trust and isolation based coping. These pathways intertwined and reinforced each other, forming a psychological network underlying NSSI behavior. Conclusions Childhood trauma serves as a core risk factor for NSSI, establishing NSSI behavior through "intertwined cognitive, emotional, somatic and interpersonal" pathways. Effective intervention should adopt an integrated approach incorporating cognitive restructuring, emotional regulation training, trauma recovery, and the social support reconstruction.