Lithium disilicate has been widely used as a restorative material because of its superiority in terms of esthetics and physical properties. Especially, single-appointment treatment using CAD/CAM has attracted much attention in recent years. From this kind of circumstance, a novel lithium disilicate glass ceramic (Initial LiSi Block) which does not require the crystallization process after CAD/CAM fabrication has been developed. In this study, the geometric crown cases which was designed by 3D CAD were fabricated by CAD/CAM system and their accuracy were evaluated. Three different types of lithium disilicate glass ceramic blocks were tested. Initial LiSi Block (LS, GC Corp.) does not require a crystallization process after fabrication, while IPS e.max CAD (EM, Ivoclar Vivadent) and CEREC Tessera (TE, Dentsply Sirona) require that process. The STL data of the geometric crown was created using CAD software. The crowns were fabricated from the lithium disilicate glass ceramic blocks using a CAD/CAM machine (CEREC MC XL (Production repeatability: 25 m), Dentsply Sirona). After fabrication, EM and TE ware crystallized or glazed by heat treatment using a furnace (Programat EP 5000, Ivoclar Vivadent) according to manufacturers instructions. The accuracy of the geometric crown was measured using an optical precision measuring machine (ATOS Capsule, GOM) (n=3), and the accuracy was compared by superimposing the fabricated crowns and the original STL data. The data was analyzed with one-way ANOVA and Tukeys tests (p < 0.05). The figure shows the accuracy (Percentage within 25 m, which is the repeatability of CAD/CAM machines) between the crown and STL data for each sample. LS had an accuracy of 63.2% within 25 m. The accuracy of EM decreased from 53.6% to 27.2% because of crystallization. TE had an accuracy of 25.0% before heat treatment, and the accuracy was equivalent to EM after heat treatment. EM requires heat treatment at high temperature for crystallization after fabrication. Therefore, it is thought that the dimensions were deformed during the process of lithium metasilicate becoming lithium disilicate. TE is took longer grinding process time. This means TE is difficult to grind and it may affect to accuracy. Thus, TE is considered that it could not be grind it accurately in accordance with the STL data, and the lower accuracy values were obtained. It was suggested that LS can obtain an accurate workpiece because LS has good grinding properties by CAD/CAM machines and does not require crystallization process and glaze firing process.