A type of controller for fruit synchronous tracking and auto-classification was developed. The results of image processing were sent to the parallel port of computer from a shift register. Certain pulse signals from sensors were taken as the shift signals, and the positions of processing results in shift register keep the same pace with that of every fruit on the fruit grading line. In this way, the synchronous tracking of fruits was realized. Meanwhile, an effective method to control the pulse distribution and correlation action of step motors, which were used to drive the grading mechanism, was also developed.