Abstract: The Court of Arbitration for Sport (CAS) has continuously used precedents in arbitration, but it never recognizes the status of precedents. This contradictory position has led to the lack of unified standards for using precedents and the differences in the results of similar cases, which has made it difficult for subsequent arbitration and athletes to understand the rules. Therefore, this study tries to construct the CAS precedential system from a two-level theoretical perspective. One is the macro level, including the theory of the Lex Sportiva and the quasi-judicial nature of sports arbitration. The second is the micro level, that is, the constituent elements of the system, which can be divided into substantive elements and normative elements: the former contains judgment standards and methods, while the latter contains ruling points and reasons. In addition, there are corresponding supporting systems as a restrictive mechanism to ensure the flexibility of the precedential system in the application. The operation of the CAS precedential system does not require the arbitration tribunal to use precedents, but is committed to enhancing the fairness and justice of the arbitration process and results in a unique form. In addition, the construction of the CAS precedent system can provide reference for the China Commission of Arbitration for Sport in terms of system and practice, and provide inspiration for the arbitration parties in China in improving their rights protection ability and preparing evidence.