Abstract: In view of the problem that traditional mine-used 127 V integrated protection systems have shortcomings of short protection distance,poor stability and inaccurate display,a digital mine-used 127 V integrated protection system based on C8051F020 was designed on the basis of analyzing protection and self-checking functions which the system should have.The system’s design of hardware circuit and software were introduced in details.The system can realize integrated protection and control functions for three circuits,meet demand of long distance protection,and reduce probability of safety accidents caused by system fault because of self-checking function.The experiment result showed that the system has full functions and low cost,and can meet needs of a modern coal mine.