This system design take at89S51 chip as core controlling element,auxiliary by necessity peripheral circuit,designed one to have retakes courses with replays the function to retake courses machine,it by 5V direct-current power supply power supply.This system adds on one in the ordinary playback's foundation to retake courses the key to carry on the control.The control function including presses down retakes courses the key control circuit to store in the monolithic integrated circuit through a/D transformation chip gathering voice signal,presses retakes courses the key to carry on retakes courses the playback,presses again puts the key to start the normal playback.A \ the D sampling circuit uses ADC0809 to realize,D \ a switching circuit uses DAC0832 to realize,and the postpositioned power amplifier actuates the speaker work.The present paper mainly introduced retakes courses machine the software and hardware part's design,as well as the question which and the solution in the design,the debugging process meets. This system design take at89S51 chip as core controlling element,auxiliary by necessity peripheral circuit,designed one to have retakes courses with replays the function to retake courses machine,it by 5V direct-current power supply power supply.This system adds on one in the ordinary playback's foundation to retake courses the key to carry on the control.The control function including presses down retakes courses the key control circuit to store in the monolithic integrated circuit through a/D transformation chip gathering voice signal,presses retakes courses the key to carry on retakes courses the playback,presses again puts the key to start the normal playback.A \ the D sampling circuit uses ADC0809 to realize,D \ a switching circuit uses DAC0832 to realize,and the postpositioned power amplifier actuates the speaker work.The present paper mainly introduced retakes courses machine the software and hardware part's design,as well as the question which and the solution in the design,the debugging process meets.