With the advantages of high power density, high efficiency, high controllability, and low noise, brushless DC motors (BLDCMs) are especially suitable for mini unmanned underwater vehicle (UUV) whose interior space is strictly limited. Hardware miniaturization design is carried out for the power drive system of mini UUV. On the premise of meeting the power requirements, the integrated functional chips are used to reduce the space of functional module to achieve the compactness of the control circuits and drive circuits of the system. It is verified by experiments that the speed control accuracy and load performance of the drive control system with satisfactory compactness can meet the requirements of the mini UUV.