Objective: Explores the major effect factor of middle-school students’ Internet Overuse Tendency (IOT). Methods: Diagnostic Questionnaire for Internet Addiction (YDQ), Strength and Difficulties Questionnaire (SDQ), Eysenck Personality Questionnaire (EPQ), the screen for child anxiety related emotional disorders (SCARED), Family Assessment Device (FAD), and the Self-Esteem Scale (SES) were used to investigate 2252 middle school students. Results: Tendency group was more obvious than control group in total difficulties, anxiety, neuroticism, hyperactivity, intercourse problems, defect degree of difficulty, family total function, behavior problems, but was less obvious than control group in self-esteem, prosocial behaviors (P < 0.001). The regression analysis indicated that total difficulties, neuroticism, self-esteem were important factors (P < 0.001), explaining 29.9%. Conclusion; For IOT prevention and intervention, we should not only pay attention to solve their practical difficulty, but also enhance self-esteem.