Objective To investigate the mental health status of the junior left-behind in the southwest of Guizhou province,and provide scientific advice for teens to cultivate a healthy personality. Methods With stratified random sampling Method,492 junior middle school students were extracted as the research object,among which 272 left-behind students as study group and 220 non left-behind students as control group.The self-designed general condition questionnaire and Self-reporting Inventory (SCL-90) were used as investigating tools.The each factor score of SCL-90 were compared between the two groups and intragroup. Results 1)The differences of score of each SCL-90 factor between left-behind and non left-behind were significant (P＜0.05).2)The scores of the left-behind boys were lower than those of girls in interpersonal sensitivity,gloomy and anxious,the differences were statistically significant (P＜0.05);The scores of factor of the only child left-behind children were higher than those of the non-only child in obsessive compulsive symptoms,gloomy,anxious,hostile,horrible,stubborn and psychotic,and the differences were significant (P＜0.05).4)The difference of left-behind time had influence on the left-behind,and the difference was statistically significant (P＜0.05). Conclusions The mental health status of left-behind is worse than non left-behind;The psychological problems of left-behind girls is poorer than of boys;The mental health level of the non-only child left-behind is higher than the only-child;The longer of the left-behind time,the higher of the psychological problems.