The invention relates to an adjustment actuator, in particular to an actuator for adjusting a guide vane of a hydraulic torque converter. The actuator comprises an actuator mounting seat, an active guide screw axis, a guide sleeve, a bearing positioning sleeve, a pin, a sleeve, and a synchronous turntable. The actuator mounting seat is connected with an adjusting mechanism support seat; the active guide screw axis is installed in the adjusting mechanism support seat; a screw rod is located in the active guide screw axis; the bottom of the active guide screw axis is connected with a nut; the bottom of the screw rod is connected to a connecting rod through a short pin shaft; the connecting rod is connected with an actuator connecting block through a long pin shaft; the synchronous turntable is located at the end part of the actuator connecting block; the top of the active guide screw axis is provided with an actuator connecting plug-in component. The actuator provided by the invention is simple in processing, convenient in installation and disassembly, small in volume, light in weight, high in control precision and fast in response, and it can control the opening degree of the guide vane of the hydraulic torque converter reliably for a long time.