A method of adaptively controlling a brushless DC motor includes steps of: controlling the brushless DC motor rotating at a first speed according to an operation curve, accumulating a running time of the brushless DC motor, estimating a remaining used time of a bearing of the brushless DC motor according to the accumulated running time, executing an alarm operation when the remaining used time is less than a predetermined time, and decreasing the speed of the brushless DC motor to run at a second speed to prolong the used time of the bearing.