Abstract: The system of automatic grading and defect detection of tiles based on LabVIEW is studied, in which the technology of the computer visual and digital image processing are applied. The system is made up of PXI-bus controller and image acquisition equipment using IEEE-1394 interface. The main algorithm is developed under IMAQ Vision Assistant at first. Then it is configurated into LabVIEW procedure after the algorithm’s rationality is validated. At last the procedure is modified and the interface is developed under the LabVIEW, which are more flexible and more humanistic. The system can do automatic grading and defect detection online on tiles. And the detailed reports about defect detection are gained.