An intelligent channel allocation method is used for detecting and avoiding a second wireless communication system taking advantage of the characteristic of a first wireless communication system in two different wireless communication system. The first wireless communication system features a narrower bandwidth, while the second wireless communication system has a non-fixed length of a frame for sending/receiving or a broader bandwidth. When these wireless communication system use a same radio frequency (RF) band, the carriers used by them are overlapped. To avoid the mutual interference, the first wireless communication system uses a background scanning mechanism to simultaneously detect the second wireless communication system and a presence range of the second wireless communication system is decided, followed by executing a handover scheme.