Objective To investigate the interface bond and thermal compatibility between Mark Ⅱ machining ceramic and Vita VM9 veneering porcelain. Methods A bar shaped specimen（30 mm×15 mm×1 mm in size） of Mark Ⅱ block was prepared, with 0.5 mm-deep notch（vertical to the long axis of specimen） at the middle of the bottom surface. The upper surface was veneered with 0.3 mm VM9 dentin base porcelain. Then the specimen was fractured from the notching site and the fracture surface was examined under scanning electron microscope（SEM） and electron microprobe analyzer（EMPA） with electron beam of 1 μm in diameter. Another ten specimens（30 mm×15 mm×1.5 mm in size） were fabricated and the temperature of thermal shock resistance were tested. Results SEM observation showed tight bond between these two materials and EMPA results showed penetration of Al element from Mark Ⅱ block into veneering porcelain and Ca element from veneering porcelain into Mark Ⅱ block occurred after sintering baking. The average temperature of thermal shock resistance for specimens in this study was（194.0±10.3）℃. Cracks were mainly distributed in veneering porcelain. Conclusion Chemical bond exists between the Mark Ⅱ machining ceramic and Vita VM9 veneering porcelain, and there is good thermal compatibility between them.
