In this study, an improved quench testing method for thermal shock resistance has been proposed. Repeated thermal shock tests were performed on cemented carbides to show the advantages of the new proposed method that would enable us to estimate an intrinsic relationship between the crack propagation rate and the stress intensity factor under repeated thermal shocks. The cyclic thermal fatigue crack propagation behavior and fracture toughness values were shown to be independent of the specimen heights and the cooling media employed. We then evaluated the thermal crack propagation behavior for cermets and cemented carbides by using this method, and discussed the differences between both materials in the crack growth behavior on the basis of their microstructures.