A method of switching a radio resource mode allocated to a mobile station in a wireless access system is discussed. The method for switching the radio-resource mode allocated to a mobile station in the wireless access system includes, transmitting a first message comprising Carrier to Interference and Noise Ratio (CINR) information of a second radio-resource mode to a base station for requesting a switching from a first radio-resource mode allocated to the mobile station to the second radio-resource mode; and transmitting a predetermined codeword for indicating that the switching from the first radio-resource mode to the second radio-resource mode has not been normally performed, if a second message approving the switching of the radio-resource mode is not received within a predetermined time.