In order to improve the efficiency of steel ball diameter detection in small and mediμm-sized enterprises and reduce the investment of capital, a method of steel ball diameter measurement based on machine vision was presented. First, the working principle of the system was given; secondly, the core hardware was designed and the hardware parameters were given; finally, the experimental platform was built. When the designed system was used to measure steel ball with diameter of 6mm and 8mm, the standard deviation is less than or equal to 0.007mm, and the repeatability precision approaches 0.023mm. The linearity of the system is ideal when measuring the diameter of steel ball from 6 to 8mm. The experimental results show that the system can be used for high-precision and non-contact detection of steel balls of grade G100 or below.