It is of great practical significance to explore the impact of the Internet use on the development of adolescents' literacy. Based on the survey data from Programme for International Student Assessment (PISA) in the four provinces of Beijing, Shanghai, Jiangsu and Guangdong in 2015, this paper used the propensity score matching method to control the sample selection bias, and examined the impact of Internet use on students' academic literacy and the moderating effect of Internet use motivation. This study found that after controlling for students' psychological and behavioral characteristics, school network environment and family background, students who spend more than six hours on Internet outside of school on a typical weekday showed significantly lower mathematical, reading and scientific literacy. The influence of internet use on students' academic literacy is increasing with the increase of online entertainment frequency. The lower literacy caused by Internet addiction mainly exists in rural areas among the disadvantaged groups with lower economic, social, and cultural status, which results in the expansion of educational inequality. Further, the negative effect of Internet addiction on the development of adolescents should be paid attention to by policy makers.