Provided are a method for accessing a wireless local area network, a terminal device, and a network device. The method comprises: a terminal device sends a system message request to a network device, the system message request being used for requesting the network device to send a system message to the terminal device, and the system message being information for accessing a wireless local area network by the terminal device; and the terminal device receives the system message sent by the network device. In the method for accessing a wireless local area network in an embodiment of the present invention, for a 5G communication system, part or all of traffic can be transferred to the WLAN or an unlicensed frequency band by adding system information, thereby saving licensed frequency band resources.