The invention discloses a multimodal-medical-image-based auxiliary diagnosis system and method for the Parkinson's disease. The system is composed of an input module, a feature extraction module, a feature fusion module, and a diagnosis module. In addition, the method includes: after an ultrasonic image, an MRI image and a PET image are obtained, feature extraction is carried out on the data of three channels by using different methods, and feature fusion is carried out on the extracted features by using different fusion methods; the diagnostic module processes the features of three modes by means of integrated learning to obtain a diagnosis result, so that an auxiliary reference is provided for the diagnosis by the doctor. For the exiting early-stage diagnosis of the Parkinson's disease,the multimodal data are analyzed quantitatively, so that the system and method have the important significance in the early diagnosis of the Parkinson's disease; and the accuracy of diagnosis is improved and the subjective determination error of the operator is reduced. Moreover, the early clinical intervention is realized and thus the post-stage disability is reduced, so that a certain auxiliaryguidance effect is realized.