The invention relates to a testing block used for measuring a refraction angle of an ultrasonic inclined probe. The testing block is characterized in that the testing block comprises a bottom surface and a vertical surface, which are mutually perpendicular, a first circular arc positioned between the bottom surface and the vertical surface as well as a front side surface and a rear side surface, which are positioned on the front side and the rear side, wherein the first circular arc is an inward convex quarter inner circular arc; angle scales are engraved on the edge, near the first circular arc, of the front side surface or the rear side surface; the angle scale value represents the angle between the connecting line from the scale point position to the center of the first circular arc and the vertical surface.