For the problem that the noise level of some combine harvester doesn’t match the national certification, combining partial coherence, transfer path analysis and the theory relate to correlation and coherence, the new method of identifying multi-correlated noise sources is developed.The characteristics of sound source and independence of signal which have mutual interference each other are analyzed and computed with developed partial coherence method, simultaneously,using TPA(Transfer Path Analysis) method, the sound source relate to engine of combine harvester is analyzed, finally, the major noise source location of the harvester is identified, and the energy contribute of source to the target is known. After the major structure of noise source being improved appropriately, the level of ear noise meets the requirement of national standard in real experiment.