Embodiments of this disclosure include a channel access method in a wireless local area network (WLAN) and related apparatus. In the method, a communication device receives a first overlapping basic service set (OBSS) frame on a primary channel, determines a first channel with a busy channel state based on bandwidth information carried in the first OBSS frame, and performs channel contention when switching from the primary channel to a second channel. After the communication device backs off to 0 on the second channel, the communication device determines a third channel used for transmitting data, where the third channel does not include any sub-channel of the first channel, and the first channel includes the primary channel.