Abstract: This study explores the relationship between perceived social support and non-suicidal self-injury (NSSI) in adults, and the mediating role of negative emotions and loneliness. In July to September 2024, a total of 1751 adults were conducted by questionnaire survey in Nantong. The survey included the Depression-Anxiety-Stress (DASS-21), Loneliness, Perceived Social Support (PSSS), and non-suicidal self-injury. The results showed that the detection rates among adults were 5.08% for NSSI, 5.88% for stress, 8.00% for anxiety, 6.74% for depression and 7.76% for loneliness. The score of social support was 64.09 (SD=8.72), which was at a high level. Mediation analysis revealed that negative emotions and loneliness play mediating roles between perceived social support and NSSI. The results indicate that high perceived social support levels can not only directly reduce the occurrence of NSSI in adults but also indirectly decrease its incidence by alleviating individual negative emotions and loneliness.