The present invention relates to a wireless access system, and more particularly, to a method and apparatus for transmitting data signal by using a massive Multi Input Multi Output (MIMO). In one aspect of the present invention, a method for transmitting data signals by using a massive Multi Input Multi Output (MIMO), the method is performed by a transmitter and comprises steps of inputting input bits of data signals to a channel encoder; outputting from the channel encoder a first coded bit set including one or more coded bits and second coded bit sets including one or more coded bits; transmitting first data signals of the first coded bit set by applying a first MIMO mode; and transmitting second data signals of the second coded bit sets by applying a second MIMO mode.