The present invention relates to an improved assembly of driving device for brushless motor of air-conditioner, which is a design providing a unitary and simple assembly of driving device of brushless motor, including a brushless motor body and a support rack. The support rack is made in the form of a U-shape having opposite ends forming end plates that extend high upwards. Besides providing a recess for positioning, assembling, and fixing the motor body, the U-shaped support rack forms a space that exactly accommodates the driving device therein, whereby the structure of the motor is reduced in volume and the purposes of use of simplified structure and practical convenience are realized.