Porcelain inlay preparation is very important, porcelain inlays require the preparation of the tooth surface is very smooth, rounded without very sharp edges, that is to say, the preparation of all points, lines, surfaces need to be a gentle surface. And the requirements of the real tooth tooth decay part, defective part are ground off, if the tooth formed a deep concavity, the need to remove the inorganic enamel above the concavity, so that the axial angle in the middle of the inlay, to maintain a 90 degree edge direct contact. In addition, the porcelain inlay edge and the tooth edge are required to intersect at a right angle of 90 degrees, not to prepare a 45-degree cavity edge bevel, the deepest part of the cavity bottom to the tooth occlusal surface of the thinnest distance to be greater than 1.5 mm, the narrowest part of the inlay to be greater than 2.5 mm, and to set aside sufficient tooth tissue, to retain the tip of the tooth at least 1/3, so that the porcelain inlay tooth preparation step is complete. If the inlay is made for a dead pulp tooth, usually the preparation is a high inlay, high inlay requires all occlusal surfaces to be covered, that is, the inlay occlusal surface should cover all the cusps, then it is necessary to prepare the occlusal surface of the abutment teeth by about 2.0 mm, lowering the height of the cusps by 2.0 mm, so that the occlusal surface of the high inlay covers the entire occlusal surface.