Abstract: Through the principle of rapid measurement of cast iron’s Brinell hardness which was based on depth measuring method, the factors which affected the measurement accuracy were analyzed. Compared to empirical data and standard sample method, the scheme of using inspection samples was used to collect the original data. Then amounts of actual sample tests were taken to verify the original conversion table of indentation depth and hardness. By the hardness comparison of indentation depth measuring and optical indentation diameter measuring, the cause and the solution of error were analyzed. By increasing the data density on both ends of the measuring range and their distribution uniformity, the accuracy of rapid measurement of cast iron’s Brinell hardness could be improved effectively based on keeping the measuring speed and automation level.