The present invention relates to a control technology of a three-phase DC motor. In order to resolve a problem in the prior art that the good current closed-loop control has not been realized on a three-phase square-wave brushless DC motor, the present invention provides a brushless DC motor control system, wherein cathodes of freewheel diodes D1, D3 and D5 are independent of input terminals of their respective switch tubes and connected in parallel to a sampling coil L1, and anodes of freewheel diodes D4, D6 and D2 are independent of output terminals of their respective switch tubes and connected in parallel to a sampling coil L2. The present invention can use a single resultant current sensor to completely and continuously sample the three-phase current existing during the motor is on and performs current freewheel, and perform the continuous closed-loop control on the three-phase current with a single current closed-loop regulator, thereby increasing dynamic and static indexes of the motor significantly.