Based on the discussion of MCU technology and its application in online test and process equipment for vehicle & motorcycle's accessory recent years,the paper elaborates the function of online test and process equipment for vehicle & motorcycle's accessory,brings up the hardware and software developing method which is applied to the C8051F020 MCU in electric controlling module of online test and process equipment for magneto.The test equipment has been made and tested the application effect of the MCU technology,on which works on with the real magneto product on line test in the factory,and this detected equipment is stability,unfailing apparatus through the real test.