In the actual industrial production,there are more and more demands for the dimension measurement of parts with multi circular arc symmetry.However,most of the traditional contact measurement methods have some shortcomings such as unstable measuring accuracy,easy to damage parts and low efficiency.Therefore,based on the principle of non contact measurement of machine vision,this paper firstly builds a dual telecentric machine vision measurement system to collect effective part images.Then,the sub pixel edge detection algorithm is used to extract the sub pixel edge of the image,combined with the least square method and the custom Halcon operator of the multi circular arc fitting of the internal tangent circle,the precision measurement of the multi circular arc symmetric parts is finally realized.To verify the effectiveness of the designed system,the stability and repeatability of the inner sleeve of a ball cage coupling are measured.The experimental results show that the measuring precision of the system can reach 0.01mm,and the measuring process is fast and stable.