Based on the China Education Panel Survey 2017-2018 school year baseline data and 2018-2019 school year follow-up data, this paper forms short panel data, and uses the unconditional fixed effect panel quantile regression method to discuss the impact of home computer and Internet on junior high school students’ cognitive ability. The results show that: firstly, home computer and internet have significant improvement effect on junior high school students with moderate cognitive ability. Secondly, Parents’ discipline on junior high school students’ use of computers and the Internet has an inverted U-shaped on their cognitive development as a whole. Thirdly, for junior high school students with low level of cognitive ability, the quality of the school is more important to their cognitive ability development. Fourthly, “expectation friction” between junior high school students and their parents’ educational expectations will limit the development of junior high school students’ cognitive ability as a whole. According to this, on the one hand, the government should implement the access and use of junior high school students’ home computers and the Internet. On the other hand, parents should play the role of guidance and supervision in the process of junior high school students’ using home computers and Internet, communicate in a timely manner, and create a good environment for the students’ use of home computers and Internet.