Objective: To conduct a comparative study on the specific effects of systematic sex education on adolescent students in terms of sexual cognition, sexual values, and sexual adaptation, and to provide the support for conducting a comprehensive education in middle schools. Methods: A whole group sampling method was used to select 3 369 middle and high school students from six general and vocational middle schools in Sichuan Province, which were divided into systematic sex education schools and non systematic sex education schools, and a comparative study was conducted using the Adolescent Mental Health Scale. Results: The results showed that the adolescent students who received systematic sex education were significantly different from those who did not receive systematic sex education in terms of sex related cognition (7.18±6.24, 5.65±7.40), sexual values(7.60±1.17，7.30±1.24), and sexual adjustment (11.49±1.29，11.10±1.41). All differed significantly ( t =5.95, 6.80,7.57, P <0.01). The students who received systematic education in junior middle school were higher than those who received non systematic education in sex related cognition, sexual values and sexual adaptation ( P <0.01). However, in senior high school, the differences in systematic education are only shown in sexual values control and self adaptation in sexual adjustment ( P <0.01). There were significant differences in sex related cognition, sexual values and sexual adjustment between male and female students who received systematic education and non systematic education ( P <0.01). Conclusion Systematic sex education is more beneficial to the psychosexual health of adolescent students than non systematic sex education in schools.