The invention provides a man-machine motion interaction system and method based on expression recognition. The system comprises an image acquisition module, an image processing module, an expression recognition module, a man-machine interaction module and a storage module. The image acquisition module acquires a facial image; the image processing module processes the acquired facial image for graying, size adjustment and the like; an expression in the facial image is recognized by means of expression recognition; the man-machine interaction module feeds back to a user according to the facial expression; the statistical and storage module analyzes mental state of the user at this moment and records the mental state; meanwhile, a statistical query function is provided for the user. After applied to intelligent equipment, the system is capable of providing specific humanized responses so that the equipment can be more intelligent; when applied to mental care robots, the system is capable of capturing patients' expressions to allow for simple and effective communication with patients, so that the patients with mental illnesses can be supervised safely in real time, and effective data basis for treatment is provided for doctors.