The invention relates to a device for automatically grading pearls on line according to the size and the shape on the basis of monocular multi-view machine vision. The device comprises a flow line, a monocular multi-view machine vision device and a microprocessor, wherein the flow line is used for automatically detecting and classifying pearls and comprises a feeding action mechanism, an inspection action mechanism, a discharging action mechanism, a classifying action mechanism and a classifying execution mechanism; the multi-view machine vision device is used for shooting images of pearls to be detected; and the microprocessor is used for carrying out image processing, detecting, identifying and classifying on the pearls to be detected and coordinately controlling coordinated action of the action mechanisms. The device for automatically grading the pearls on line according to the size and the shape on the basis of the monocular multi-view machine vision, disclosed by the invention, has the advantages of simple mechanism, low manufacturing cost, capability of meeting the detection of quality indexes, such as size and shape, high grading efficiency, convenience for use and maintenance and high automation degree.