A method for guaranteeing a data frame transmit opportunity in a wireless LAN system having three different transmission modes includes: setting a first transmission protection interval based on a lowest transmission mode, when a node of a mode having a lowest transmission rate among the three transmission modes exists in the wireless LAN system, aggregating a data frame to be transmitted within time of the set transmission protection interval, and transmitting the data frame; and setting a second transmission protection interval based on a mode having a highest transmission rate, when only nodes of a mode having a highest transmission rate among the three transmission modes exist, aggregating a data frame to be transmitted within time of the set transmission protection interval, and transmitting the data frame.