An access control method, system, and a switch, pertains to the field of network technologies. The access control method includes receiving, by an authentication device, a packet from an access device, where the packet includes a virtual local area network (VLAN) identifier, and authenticating, by the authentication device based on the VLAN identifier and a preconfigured correspondence using an authentication method corresponding to the VLAN identifier, a terminal device sending the packet, where the correspondence includes a mapping from a plurality of VLAN identifiers to at least two authentication methods. Hence, the authentication method of the terminal device is determined based on the VLAN identifier such that different authentication methods may be used for terminal devices in different VLANs. Therefore, an access manner is flexible.