Abstract: Platform rules are the basis of platform operation, and the legality control can prevent and regulate the improper behavior of platform operators. The legitimacy control of platform rules needs to pay attention to the characteristics of platform organization, behavior power and operation technology. Affected by the operation of the above platform rules, platform operators and users lack a reasonable negotiation context and can directly affect the rights and interests of users with the help of algorithms and other technologies, and users lack the consciousness and ability to protect themselves. In this context, the legality control of platform rules should take into account the dual attributes of “power” and “market” of private power by means of public and private laws and regulations, strengthen the administrative filing mechanism, users' democratic participation and internal compliance of platform enterprises, and ensure the legality of the operation procedures and entity contents of platform rules.