Radial runout is a major performance parameter of running accuracy of bearings. In order to increase the running accuracy of cylindrical roller bearings, a new algorithm is presented. Firstly, the principle of program is researched under some suitable conditions. Secondly, the process and structure of program is described in detail. In the end, the influence of the size of roundness error on the radial runout of bearings is researched. The results show that the radial runout increases 7 times higher with the increase of roundness error size of outer ring.