To realize the high speed and low cost measurement of the wall thickness of the wax pattern of a turbine blade, a novel wall thickness calculation method is proposed based on the inscribed circle chord length between the inside and outside contour lines of the wax pattern wall. First, the optical scanning data registration of the wax-pattern and the ceramic core is studied, and the contour lines are extracted from the registration model. Then, two different computing models for the inscribed circle chord length of the contour lines are built. Finally, a sample application is presented for demonstration by comparing the method in this article with the computer tomography (CT) measured data. The result shows that the wall thickness calculated by the inscribed circle chord length method agrees well with the CT measured data.