ObjectiveTo construct a strategy for classification of clinical research data security for real-world research, based on the features of clinical research data.MethodsBased on the laws, regulations, and data security classification method in relevant fields, the clinical research data was classified into five security levels. Then, the method was gradually perfected through three times of revisions, which followed the advice from experts who were experienced in many relative areas, such as clinical medicine, clinical research methodology, clinical research management, ethics, genetics and public health data application and management.ResultsExperts’ opinions gradually converged through several times of consultation. The clinical research data was finally classified into five security levels with explicit definition and security policy for each security level. Thirty-three data categories, which covered demographic information, clinical examination, diagnosis, treatment information, genetic information, health economics information, medical data and information on research processes that have been published, were included in the five security levels.ConclusionsSince there is an increasing trend of data scale and the data security classification and management are necessary to ensure the data security and appropriately utilization of data. The method of clinical research data classification proposed in this paper can provide beneficial references for the further improvement of data security in the future.