The site characterization should be conducted during the entire decommissioning period to verify the compliance with regulatory guidance and to demonstrate the safety for site release. A technical manual called Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) has been widely used as a reference for the site characterization. Historically, it has required enormous resources because of extensive data handling. And there is a possibility of a human error because of the expert’s judgement reliance. In this study, software called COde for Site characterization and Management of Overall Surveys (COSMOS) has been developed with Artificial Intelligence (AI) models. One of the AI model is possible to revolutionary reduce time for finding keyword related contamination, and the other manages database by digitalizing drawings. Also, other survey modules are possible to conduct related all of statistical tests. In the end, COSMOS would be utilized as a total management solution for site characterization.