The invention discloses a manipulator with two-stage compliant power transmission and a grasping method thereof, and relates to manipulators. The manipulator includes a housing, a main motor, an adjustment mechanism, a transmission shaft, a transmission screw, a paw, a visual sensor, a control module and a technological parameter library module; the adjustment mechanism comprises a torque adjustment motor; the transmission shaft is in power connection with the adjustment mechanism, and one end of the transmission shaft is connected with an output shaft of the main motor; one end of the transmission screw is connected to the other end of the transmission shaft; the transmission screw provides power for the paw; the visual sensor is used for obtaining the outline size of an object to be grasped; the control module is used for controlling the main motor and the torque adjustment motor; and the technological parameter library module is used for inputting properties and outline size parameters of the object to be grasped and outputting the optimal gripping force for grasping the object. The manipulator does not depend on design of a controller and external application of force signals,the optimal clamping force is determined without changing motor driving parameters, integration of two-stage positioning and clamping force adjustment functions of grasping operation is realized, thesystem structure is simplified while compliant gripping operation is achieved, and the torque adjustment efficiency is improved.