In order to solve traditional fruit grading detection system of graded speed slow, huge system and high cost, puts forward the detection system based on SOPC fruit grading, and the whole control system was integrated into a FPGA chip, which can be detached from the PC platform, greatly reduces the cost. Through the Soble algorithm to achieve the edge of the fruit image extraction, and the method of histogram of the size of the fruit to distinguish, the fruit could be accurately classified. Test results show that this system has the advantages of fast detection speed, short development cycle, and can be upgraded online, which has a good application space.