Objective To analysis the relationship among stressors,stress medi-factors and mental health of left-behind junior middle school students( JMSS) ,and to built a structural equation model on psychological stress of left-behind JMSS. Methods 1309 left-behind JMSS in rural areas in Hunan were assessed,using self-designed Demographic Data Recording Form , Adolescent Self-Rating Life Events Check List, Scale of APGAR,Perceived Social Support Scale,Simplified Coping Style Questionnaire,Eysenck Personality Questionnaire,Self-Esteem Scale and Scale of Mental Health for Chinese Middle-school Student. Results Life events (r = 0.08) influenced mental health directly,and it influenced mental health indirectly by acting on negative coping styles(r=0.01) and APGAR (r= -0.02). Social support(r= -0.02) ,self-esteem(r = 0.03) ,negative coping styles(r=0.07) ,positive coping styles (r= -0.04),P (r = 0.03) and N (r = 0.04) also influenced mental health directly. E(r = 0. 21) ,N(r = -1.87) and P(r= -0.83) and APGAR(r=0. 10) influenced mental health indirectly by the mediation of self-esteem; APGAR(r = 4. 89) influenced mental health by the mediation of social support. Conclusion Personality (P,N),life events, social support, APGAR, positive and negative coping styles, self-esteem impact on mental health of rural junior middle school students in different ways.