Disclosed are method and device for indicating a PLCP header transmission mode. A method for generating a physical layer convergence protocol (PLCP) of a data frame can comprise the following steps: demodulating PLCP header mode information based on a scrambling sequence of the received frame or information elements included in the received frame; and generating a data frame including the PLCP header generated based on the PCLP header mode information. The PLCP header mode information comprises at least one indication from a space time block coding mode indication, a guard interval mode indication, and a repetition mode indication. The invention is capable of improving data transmission efficiency by adaptively determining a transmission mode of a PCLP header to a channel situation.