Information transmission methods and apparatuses in a wireless local area network are provided. One example method includes generating a legacy signaling field (L-SIG) and a repeated legacy signaling field (RL-SIG), where subcarriers with indexes −28, −27, 27, and 28 in the L-SIG and the RL-SIG in a 20 MHz bandwidth carry −1, −1, −1, and 1, respectively. The method also includes sending the generated L-SIG and RL-SIG.