Abstract: This papier focuses on the research of faceting principles for the sweeping solids used in the Feature-Solid Modeling Tool System(FSMTS). First, "topological validity" and precision requirements of a faceting process are discussed. Then, three kinds of moving frames used by the generalized sweeping methods are analysed, and strategies to describe the variant regularities of a moving sectional contour are proposed as well. Finally, validity verification criteria of sweeping solids are proposed.