In order to reduce the detection cost and avoid human error, a diamond rough detection system based on machine vision is developed. The information of size, shape and color of diamond is detected by image processing, and a three-dimensional model of diamond raw stone which can be displayed from a free perspective is generated. The results show that the system is easy to operate in shape and color detection, the scale accuracy of size detection is 0.5 μm and the measurement accuracy of graphic is in the micron level, which can reduce the detection cost and human error.