IntroductionAs the epidemic spreads, the problem of Internet addiction disorder (IAD) stand out and getting serious. The present study aimed to investigate IAD among junior high school students during the spread of the COVID-19, and to explore the mediating role of cognitive failure between self-concept clarity and IAD, and the moderating role of mindfulness.MethodsA sample of 1,153 junior high school students from two randomly selected junior high schools in Henan Province were surveyed anonymously with Self-concept Clarity Scale (SCCS), Cognitive Failure Questionnaire (CFQ), Mindfulness Attention Awareness Scale (MAAS) and Internet Addiction disorder Test (IAT). The sample was obtained through random cluster sampling, taking classes as the clusters and students as the elements.Results(1) Self-concept clarity was negatively correlated with Internet addiction disorder; (2) Self-concept clarity not only had a direct effect on Internet addiction disorder, but also indirectly affect Internet addiction disorder through cognitive failure; (3) Mindfulness moderates the relationship between self-concept clarity and Internet addiction disorder, as well as the relationship between cognitive failure and Internet addiction disorder. Compared with low levels of mindfulness, both the protective effect of self-concept clarity and the effect of cognitive failure on Internet addiction disorder were stronger among junior high school students who were at high levels of mindfulness.ConclusionThis study constructs a moderated mediation model to explain the effect of self-concept clarity on Internet addiction disorder. It is effective to alleviate Internet addiction disorder by improving self-concept clarity and mindfulness level of the junior school students.