The invention discloses a beef quality intelligent grading system and method based on machine vision. The system comprises a beef carcass placing platform, a camera obscura with a camera and a beef quality grading module, wherein the camera in the camera obscura is used as a collection device of the beef carcass information for collecting image signals of a beef carcass to be detected on the beefcarcass holding platform; the output of the camera is connected with the beef quality grading module; and the output of the beef quality grading module is used as the output beef grading information of the beef quality intelligent grading system based on the machine vision. In the invention, a digital image processing technique is utilized to carry out relevant required processing on the collected cross section image of the beef carcass; three indexes, such as marbling, fat color and red beef color in an effective musculus ocularis area are utilized for analyzing, thus the whole beef carcass can be graded effectively, the shortage of misjudgement of the traditional beef grading system in which a single index is used can be overcome, and the accuracy and the objectivity of grading can be greatly improved.