In the design and optimization of compressor piping system， the compressor is the main source of excitation， and the acquisition of its excitation force is crucial. When the compressor is designed and supplied by a third party， it is difficult to obtain its internal structural parameters and its excitation needs to be identified by experimental test. In this paper， the equivalent excitation at the centroid of the rotor compressor is identified based on rigid body dynamics principal. Firstly， the centroid and inertia parameters of the compressor are identified based on the mass line method. The test results show that the recognition accuracy and consistency are good. Secondly， in terms of the rigid body dynamics equation， the equivalent excitation of the compressor is identified based on the vibration response of the compressor cylinder surface， the inertia parameters of the compressor and the characteristic parameters of the rubber feet. Finally， the finite element simulation is carried out to validate the identified excitation force. The acceleration obtained by the simulation agrees well with the experimental results. The maximum error occurs in the second order of the y direction， which is 26.3%， indicating that the recognition accuracy is convincing. The identified excitation is accurate enough to be applied in the design and optimization of piping systems.