Abstract: In view of the mining technology system of underground difficult-to-mine ore-body，the system engineering analysis method is used to study process impacting the reliability of underground mining system，determine the multiple process links of mining system combined with the actual situation，On this basis，the mathematical model of the reliability of the process system is established by using the Markov process，and calculate the reliability indexes of mining so that the system reliability is revealed well.Thus，the accuracy of calculation results is improved to some extent by calculating the failure rate and repair rate instead of the traditional algorithm of the failure rate and repair rate through using Monte-Carlo numerical simulation method.The results show:Markov process and Monte-Carlo simulation method can improve the reliability of the mining process system of the underground mining body in a certain extent，it has a theoretical guidance role in the mining plan design，strengthen the safety management，improve the efficiency of mining，and prevent accidents and so on.

Key words: Safety engineering, Underground mining technology syste, Series system, Reliability, Markov, Monte-Carlo method