Abstract: Aiming at the low working efficiency and poor precision in the round hole measurement of bimetal casting parts in a military enterprise. This paper proposes a method for measuring round holes in bimetallic castings based on machine vision. This method uses the Canny algorithm to detect the inner and outer circles of a circular hole, and by introducing the global parameter K of the contour to fit the circle to obtain the best fitting circle in the selected contour, the center and radius of the circular hole are obtained, and Out of the concentricity of the circular hole. The experimental results verify the effectiveness of this method. The measurement method improves the detection efficiency, can quickly measure the size of the circular hole, and reduces the error to 2 pixels, and the measurement error is reduced by 20%.