BACKGROUND: Military personnel face more stresses and challenges, and they are at greater risk of insomnia compared to the general population. Mental health is one of the primary ways of managing insomnia. However, there are few studies regarding the mediator in the two variables among this population. This study aimed to investigate the insomnia, mental health literacy, and mental health in young soldiers, to explore the correlation of the three variables and to verify the mediating role of mental health literacy between mental health and insomnia. METHODS: The cross-sectional study was conducted from March 2023 to March 2024. A total of 2375 soldiers was surveyed using the General Information Questionnaire, Insomnia Severity Index (ISI), 12-Item General Health Questionnaire (GHQ-12), and National Mental Health Literacy Questionnaire (NMHLQ). The data were processed using descriptive analysis, Mann-Whitney U test, Kruskal-Wallis H test, Spearman's correlation analysis, stepwise regression analysis, and a mediation analysis. RESULTS: The questionnaire of 2297 participants was valid with an effective rate of 96.72%. The majority of participants were male (2281, 99.30%). The mean age of participants was 23.49 ± 2.51years (range 18-35). The total score of ISI was 1 (0, 5), with a high occurrence rate of insomnia at 14.85%. The mental health displayed a significant positive correlation with insomnia (r = 0.333, P<
0.001). Furthermore, the mental health literacy and its two dimensions-NMHLQ-mental health awareness (NMHLQ-A) and NMHLQ-identification and response to mental illness (NMHLQ-I) exhibited significant negative correlations with both mental health and insomnia (r=-0.346∽-0.074, P<
0.001). Before and after adjusted control variables, the NMHLQ-A and NMHLQ-I played partial mediating role between mental health and insomnia, and the mediating effect ratios attributable to the NMHLQ-A were 17.79% and 17.41%, whereas to the NMHLQ-I were 2.33% and 2.20%. CONCLUSIONS: Our findings highlight the potential negative impacts of mental health literacy on the insomnia of young soldiers directly and indirectly. Especially, NMHLQ-A and NMHLQ-I play partial mediating role between mental health and insomnia. According to these findings, Psychological service workers can develop and implement highly individualized effective interventions to improve young soldiers' mental health and sleep quality.