Objective: To investigate the awareness of Internet based sex education and associated among middle school students, and to provide scientific basis to improve sex education using online resources. Methods: By using stratified cluster random sampling method, 449 students from 8 middle schools in Zhejiang Province were investigated with a self designed questionnaire by Chi square test, Logistic regression, and Importance Performance Analysis (IPA). Results: The awareness of Internet based sex education was 66.59%(299), among which 17.15%(77) chose "WeChat", 7.35%(33) chose "sex education website", and 42.09%(189) chose"video platform" as the primary resources of online sex education, respectively. In the sexual health literacy of middle school students, the correct rate in sexual safety and sexual assault was higher than 40%, with STD transmission and prevention higher than 70%. The correct rate was more than 80% when it came to sexual physiology and sexual development. Logistic regression analysis showed that higher score of sexual health literacy was associated with higher awareness of Internet based sex education ( OR =1.06, 95% CI =1.01-1.11, P <0.05). According to the IPA, the teaching effect and content in area A (the dominant area) had higher scores of importance and satisfaction.The funniness of content in area B (retention area) had a lower importance score and a higher satisfaction score. The practicality and interactivity in area C (opportunity area) had low scores of importance and satisfaction. The curriculum model in area D (improvement area) scored higher in importance and lower in satisfaction. Conclusion The awareness of Internet based sex education needs to be improved among middle school students. Efforts should be made to improve sexual health literacy. Online platforms providing sex education should focus on improving the relevant course model, strengthening the practicability and interactivity of the course, and continue to maintain the advantage of teaching effect, teaching content and interesting aspects of the course.