Abstract: A new measurement method of straight slot tap radial comprehensive multi-parameter based on vision principle was proposed aiming at the problems of single measurement parameter and manual operation in the current tap measurement method. The radial profile map of the tap in polar coordinates was obtained by preprocessing. The end and core diameters were obtained by fitting a circle to the pixel with the maximum and minimum polar diameter back to the geometric center of the end edge. By fitting the characteristic curve, two pairs of line equations were obtained, and the angle formula was used to obtain the front angle and back angle values. The width of the edge back was obtained by calculating the distance between the first and last pixels of the edge back. The pole diameter difference of the first and last pixel of the edge back was taken as the shovel back amount. The experimental results show that the relative errors of the above geometric parameters are within 0.58%, and the average time is 7 s, which can meet the engineering requirements of high-precision, high-efficiency and multi-parameter automatic measurement.