Abstract: The objective of inspection, testing and supervision of medical devices is to ensure the effectiveness and safety of medical devices in clinical use. Leachable substance is the substance that can be released from a medical device or material during clinical use. Leachables are important factors for the safety risks of medical devices. The analysis, quantification, and safety evaluation of leachables are important parts of the safety evaluation of medical devices. The allowable limits for leachable substances which established from the toxicological research provides a scientific basis for the judgment of qualitative and quantitative analysis results. Obtaining more detailed, rigorous and sufficient toxicological research data is of great significance to set highly enforceable quality criteria. For the establishment of allowable limits for leachable substances, its role in the safety evaluation of medical devices is summarized, and the relevant standards and their implementation status in the testing of medical devices are introduced.