This paper focuses on the design of an intelligent 3D sensing system for product quality assurance in automated manufacturing processes. An efficient 3D object-oriented knowledge base and reasoning algorithm is developed. The knowledge base includes knowledge concerning the products, manufacturing processes and inspection methods. The knowledge-based system may be applied to such practical situations as online fault detection and automatic acquisition of a CAD model, in a manufacturing process with the objective of quality assurance of the end product. The knowledge base is regularly updated using feedback of the inspection results. An inexpensive and accurate, non-contact 3D range data measurement system is developed. The surface terrain information may be converted into the curvature, orientation, and depth of the shape to incorporate into the symbolic 3D object-oriented knowledge base and reasoning algorithms.