This application provides information sending and receiving methods and apparatuses. This application provides a new PPDU format. In some instances, a long training sequence in the new PPDU format is orthogonal to a legacy long training sequence or orthogonal to a high throughput long training sequence. By using this long training sequence, a format of a PPDU can be automatically detected, so as to further process the PPDU according to a network standard corresponding to the format of the PPDU. In addition, when a target long training field is read, the format of the PPDU can be detected, thereby, in at least some implementations, saving time for detecting the format of the PPDU, improving efficiency of detecting the format of the PPDU, and completing a task of detecting the format of the PPDU as early as possible.