A design scheme of on-line measurement and control system for plain external grinder was put forward, which included design of hardware architecture and software program in system. The controller of system was designed by using digital signal controller (DSC) dsPIC30F6014A as the processing core and the touch screen HITECH applications, which offered a friendly man-machine interactive (MMI) system. The LVDT sensor was used for measuring device of the system and AD698 chip for signal regulating, only with the addition of a few external passive components to complete converting of displacement to direct current (DC) voltage with high degree of accuracy and reliability. The system is used in innovation of the grinder, which improves the efficiency and accuracy of machining workpiece, and lowering cost, and it gets wider application prospect.