The invention relates to a locating device for a rotary steering drilling tool of a motor pump. The locating device comprises a control device, a drive device, an oil supply device and a guide device, and is characterized in that the control device controls the rotating speed of a motor in the drive device, and the motor drives a hydraulic pump to output oil with a pressure through a speed reducer so as to convert an electrical signal into a hydraulic driving force, and finally adjusts the flow of the oil output by the hydraulic pump; the guide device comprises a three-position four-way change valve and a piston rod; and the control device also controls the three-position four-way change valve to realize operation of the piston rod such as stretching, returning and position-keeping. The locating device has the advantages that by means of a pressure provided by a micro-pump driven through rotation of a micro-motor, an internal control circuit controls a miniature solenoid valve to regulate and control different hydraulic cylinders so that differential pressure balance is kept between the hydraulic cylinders and external slurry, and then an internal piston stretches out by virtue of the pressure so as to provide greater backup power for a wing plate, thus solving the problem of limited backup power provided by the existing locating device.