Objective: To investigate the status quo and causes of left behind children’s sexual problems and behaviors during puberty, and to provide relevant educational intervention strategies. Methods: A total of 2 305 left-behind students from 3 township middle schools in Jinhu County, Huai'an were selected to send out questionnaires to understand their common sexual problems, sexual behaviors, assess to sexual knowledge, and help. Results: About 30.02% of the respondents had menstruation/spermatorrhea trouble, 45.99% had acne trouble. 20.00% had early love confusion, 10.02% had masturbation confusion. The percentage of girls with early love confusion was higher than that of boys, and that of high school students was higher than that of junior high school students; the percentage of boys with masturbation confusion was higher than that of girls, and that of high school students was higher than that of junior high school students (P<0.05). 11.97% reported verbal harassment, 16.92% had been asked to fall in love, 10.02% had been kissed, 5.99% had been sexually touched, 1.00% had been forced to have sex, 17.01% had masturbation, 7.90% had same-sex sexual activities, 6.94% had sexual behaviors, and the proportion of girls who had been teased by speech, asked to fall in love, kissed and stroked was higher than that of boys, and the proportion of boys who had been stroked was higher than that of boys (P<0.05). The proportion of sexual intercourse, sexual activity and sexual behavior was higher than that of female (P<0.05). The proportion of high school students who had masturbation, homosexual activities and sexual behaviors was higher than that of middle school students (P<0.05). In terms of access to sexual knowledge, 43.99% through the school classroom, 35.01% through books, 23.99% through the Internet, 17.01% through parents and elders. Compared with boys, girls had higher proportion of acquiring sexual knowledge from books and parents’ elders, high school students have higher proportion of acquiring sexual knowledge from school classroom and books, junior high school students have higher proportion of acquiring sexual knowledge from parents’ elders (P<0.05). After the left behind children encountered sexual problems, 31.02% from the Internet/books, and 30.02% from their yellow videos/novels. Compared with boys, girls had higher proportion of seeking help from parents (P<0.05). Compared with high school students, junior high school students had higher proportion of seeking help from parents and teachers (P<0.05). Conclusion Adolescent left-behind children are generally confused about sexual physiology and their sexual behavior is relatively open. Schools and families need to strengthen sexual health education for left-behind children to help them form scientific and healthy sexual concepts and attitudes and resolve their sexual confusion.