Abstract Nowadays, the Internet has been popular all over the world and permeated people’s daily lives. The online platforms help people get extensive information and expand their ideas. In the Internet age, people use the Internet mainly for several purposes, such as searching, entertainment, accessing to information and social interaction. Not only are adults the case, children are getting into the network. According to the Report On the Use of Children’s Network in China, about half of children have access to the Internet in preschool. Therefore, many parents are beginning to worry about the negative effects of the Internet on their children, such as cyber violence, harmful information, online games addiction and so on. Nevertheless, the positive impacts of the Internet should also be highlighted. Researchers revealed that Internet can promote education justice because people of all genders, races, and income can use the Internet to study at any time and at any place. The vast information provided by Internet can provide individuals successful experience to enhance self-efficacy, which in turn may increase academic achievement. In addition, since children’s personality is greatly influenced by the environment, they are curious about the world, this study will explore that whether openness would affect the use of children’s network. To investigate the relationships among Internet use, learning efficacy, academic achievement and openness, a survey research method was adopted in which the Network usage Questionnaire, Motivated Strategies for Learning Questionnaire, Five-factor Questionnaire for Chinese Adolescent Personality and student's academic record were administered to 425 pupils. Data were collected and analyzed with SPSS 20.0. The results indicated: (1) There was no direct predictive effect of Internet use on academic achievement, but Internet use had an indirect effect on academic achievement through the mediation effect of learning efficacy. (2) Children’s openness played a moderating role in the first half of the mediation path. For individuals with high openness, the mediating effect of learning efficacy was not significant, whereas this mediating effect was significant for individual with low openness.. These findings highlight the complex relationship of association between Internet use and academic achievement. Internet use enhances learning performance by providing a lot of information for people to gain a successful experience that improves their academic performance. Open-minded children love new things, and they are more likely to be addicted to online leisure and entertainment activities, which cannot improve learning efficacy. Therefore, parents and educators must respect the characteristics of children and guide them to rationally use the network.