The paperboard detect system of folding machine base on MCU AT89C55. It includes level transition module、unexpected action protection module、 alarm and halt module 、communication module and memory extension module in hardware design of system, It use μVision2 and WAVE6000 in software design . It replace of paperboard detect system base on PLC. It have been tested, runed placidly,reacted promptly.The system reach the require.