Abstract: The paper took high-performance DSP DM642 as core to build hardware platform of digital image processing system and used M file S-function in Matlab to develop user-difined algorithm module so as to build Simulink model of complex image processing algorithm,which realized high-speed processing for digital image.It took Canny brink algorithm as example to carry out experiment.The experiment result showed that the implementation of digital image processing in DSP platform could improve processing speed,using user-difined algorithm module of S-function could improve programme efficiency.