Abstract: A study on the internet addiction of Chinese youth by psychological scales, deep interview, brain event-related potentials (ERPs) and heart rate variability (HRV). Focus on the causations, psychopathology, diagnosis methods and psychotherapy of internet addiction. Basing on data from the investigation and experiments, these results and conclusions were received. 1. To classify the internet using problems of Chinese youth from angle of psychological developing and advanced diagnosis methods. 2. To analyze the causations of internet addiction and explain the psychopathological mechanisms by Psychological Decompensation Hypothesis. 3. To explain the brain mechanisms by attention facilitation mechanism. 4. Making the Systemic Compensation Psychotherapy Plan, including group, family, individual and parents psychological intervention. This plan obtained very good effect on the clinical study

Key words: internet addiction, psychopathology, psychotherapy