This application relates to the field of wireless communication technologies, and in particular, to a method and an apparatus for transmitting a physical layer protocol data unit, and for example, is applied to a wireless local area network. The method includes: A first communications device generates a PPDU and may send the PPDU, where the PPDU includes an LTF sequence; and correspondingly, a second communications device receives the PPDU, and parses the PPDU to obtain the LTF sequence included in the PPDU. Embodiments of this application can be used to design an LTF sequence that has a relatively low PAPR on entire bandwidth, on a single resource unit, on a combined resource unit, and in a considered multi-stream scenario.