s.The least-squares algorithm is usually used to fit data in circle detection. The application of the conventional least-squares algorithm is limited, its’ roundness error is bigger, and precision is lower. For detecting circle with data points of non-uniform distribution, developed an analysis algorithm for assessing the minimum zone roundness error. Center and radius can be accurately solved, without iteration, without truncation error. Visual measurements have been carried out for known diameter D=2.564mm tooth shape chain board’s aperture using the proposed methods, calculated results (Table 1) using four kinds of roundness error evaluation methods. Tooth shape chain board’s aperture diameter errors are 0.0157mm、0.0126mm、0.0117 mm and 0.0218mm, roundness errors are 0.0251 mm、0.0225mm、0.0228mm and 0.0244mm respectively. The minimum zone algorithm are suitable for distributed data of all kinds situation, particularly suitable for the realization of machine vision inspection system, fast speed for high precision, wide range of application.