Abstarct: Drum shearer is one of the most important and well-known machines in underground coal mining. This machine is the first component of production chain in longwall mining. In this thesis, the reliability of drum shearer has been modeled using the field time between failures data in the Tabas coal mine, Iran. The series network configuration with six subsystems including the water, haulage, electrical, hydraulic, cutting arms and cable systems have been assigned for analysis. The time between failure data was analyzed using Weibull++ and Easyfit softwares. The results showed that failure behavior of haulage and hydraulic systems follow the 3-parameters Weibull and the Gamma and lognormal distributions are the best-fitted distribution on the water and electrical systems respectively. Power Law Process model was used for cutting arms and cable system. Pareto analysis showed that the 30% of failures and stoppages of shearer is related to water system and this system is the most critical subsystem of machine. The failure rate analysis on failure data shows that the failure rate of hydraulic, haulage and electrical systems are decreasing, meanwhile, failure rate of water system, cutting arms and cable system are increasing. In this research, the 90% is selected as desired reliability level for scheduling the preventive maintenance for each subsystem of drum shearer. The combination of maintenance tasks of different subsystems shows that preventive maintenance of water system and hydraulic system should be done every 5 hours. The electrical and haulage system should be maintained every 10 and 20 hours respectively. For cutting arms and cable system, maintenance tasks should done every 90 hours simultaneously. Also, the Kamat-Riley (K-R) Event-baxsed Monte Carlo Simulation Method was used for reliability analysis of longwall shearer machine. With negligible assumption of time to repair, a flowchart was built for programming the simulation process. The Matlab mathematical programming software was used for reliability simulation process. Finally the reliability plot of longwall shearer machine was achieved and upper and lower bound reliability were calculated. The results illustrate that the reliability of shearer machine reduces to zero in a period of 100h.