A method and system for transmitting and receiving data to prevent Adjacent Channel Interference (ACI) in a Cognitive Radio (CR) communication system are provided, in which a second system using a second frequency band measures a first channel interference that a first frequency band used by a first system causes to the second frequency band, determines a frequency spreading parameter according to the first channel interference, measures a second channel interference that the second frequency band causes to the first frequency band, receives link information from the first system according to the second channel interference, determines a power allocation map according to the link information and transmits and receives data according to the frequency spreading parameter and the power allocation map.