Objective　To explore the relationship of defense style and mental health in student of middle school. Method 203 middle student were investigated with Defense Style Questionnaire (DSQ) and Symptom Check List-90 (SCL-90). Results There were no significant difference for 4 factors of DSQ in man／female and advance middle school or not(P>0.05); there were significant difference for immature defense mechanism and middle type factor ,and conceal factor in high-symptom score team with that of low-symptom sore team(P<0.01) and it is positive-correlation with each factor-score and total score of SCL-90. Conclusion School and family need to pay attention to the higher correlation in the total score of SCL-90 with immature defense mechanism and middle type factor and conceal factor.