The frame transmission method in the wireless local area network includes: generating, by an access point, a physical layer protocol data unit PPDU of a target type, where the PPDU includes a target media access control MAC frame structure that is generated in a target encapsulation format and that carries a trigger frame, and whether the target MAC frame structure includes a packet extension field is determined based on the target type and the target encapsulation format; and sending, by the access point, the PPDU. In the embodiments of the present invention, whether the target MAC frame structure includes the packet extension field is determined based on the target type of the PPDU and the target encapsulation format of the target MAC frame structure that carries the trigger frame, so as to adapt to various versions of PPDUs.