The invention provides a high-power-density integrated electromechanical servo actuating device. The high-power-density integrated electromechanical servo actuating device comprises an integrated permanent magnet synchronous motor, a rotor sleeve, a planet roller lead screw pair, a bearing and matched devices such as a sensor. A motor stator is embedded into the inner side of a cylinder body, forms the integrated motor together with a permanent magnet patch attached to the rotor sleeve and drives the rotor sleeve to do rotating motion; the rotor sleeve is fixedly connected to a flange plate through a screw and then drive a lead screw to generate synchronous rotating motion through a key structure arranged on the roller lead screw; the planet roller lead screw pair converts rotating motion of the lead screw into linear motion of a nut; finally, the nut pushes an output rod to do linear motion by taking the liner bearing as a guide of the output rod through a thread formed in the output rod and a lock washer device. According to the high-power-density integrated electromechanical servo actuating device, the problem that an existing electromechanical actuating device is large in size and weight is solved, then the power to weight ratio and loading capacity of the electromechanical actuating device are increased, and a technical support is provided for promoting development of future multi-electrochemical/full-electrochemical air vehicles.