The invention discloses a kinetic parameter on-orbit identification method and device of a satellite-arm coupling system. The method comprises steps as follows: obtaining motion state data of a motion joint of a mechanical arm and corresponding main satellite data which are measured actually and comprise main satellite attitude angles and attitude angle speed data; assuming a set of main satellite kinetic parameters; inputting the motion state data of the motion joint of the mechanical arm and the assumed main satellite kinetic parameters into a kinetic model for simulation; comparing the difference of main satellite data output by the kinetic model and the main satellite data measured actually; and then optimizing the assumed main satellite kinetic parameters with an improved global particle swarm method, wherein the main satellite kinetic parameters comprise main satellite mass, location of a main satellite mass center and main satellite rotational inertia. The kinetic parameter on-orbit identification method and device can realize on-orbit identification of the kinetic parameters of the satellite-arm coupling system and have higher universality.