This paper aimed to sort out the development and application of the diagnostic criteria and assessment tools of internet addiction through reviewing and integrating related empirical and conceptual studies. We also offer future directions for research andclinical practice on this issue. After reviewing the diagnostic criteria and related assessment tools from the threeaspects of “substance abuse”, “impulsive control disorder” and “problematic internet use”,wealso included the compensatory use and neuropsychological /neuroimaging research findingsto obtain a picture of how the diagnostic indicators developed. We found that there were many psychiatric disordersassociated with internet addiction, butits diagnostic indicators cannot be developed solely based on the perspective of mental disorder. The psychometric properties of the assessment tools were validicated by many studies, but no concensus have been reached. The application of assessment tools shifted from a single scale to a package of tools with muti-dimensions and multiple assessing methods. Based onsuch findings, we recommend toinclude the experience of internet users as the foundational concepts for understanding the phenomenon of internet addiction, and propose a conceptual model to validate its constructs and formation process. Both the diagnostic criteria and assessment tools need to be reinvestigated. The clinician should obtain information from multiple perspectives of problematic internet users’ life experincesto offer interventions focused on their motivation, needs, and behavioral characteristics.