Objective:To explore the character of the defense mechanism in high school students so as to offer reference for the mental healthy consult and instruction of middle school.Methods:231 grade two high school students were investigated with Defense Style Questionnaire(DSQ).Results:Most of the high school students inclined to use the mature defense mechanism;There was interaction between the sex and origin in the concealment facctor;city girls score the least(conceal the most)and country girls score the most (conceal the least).There were differences on sex:boys score significantly high in splitting and dissociation while in idealization girls get more than boys,Still there were differences on origin:students from country score higher than those from city on complaint and check,city students inclined to use much moer anticiation.Conclusion: As a whole,high school students incline to use mature defense mechanism,and there are differences of sex and origin on the mechanism measures.