Abstarct: Reliability as an engineering index has many applications in operations control and productivity of machinery. With regard to the high volume of operations in mines, keeping the production power and machinery management are instances which may seriously affect the economical and operational situation of the mine. The production reliability of each mine depends directly on reliability of active machinery in that mine. In a mechanized underground coal mines, the production and equipment includes four main systems: compressed air production, ventilation underground network, excavation and extraction equipment, and mine transportation. Afterward, during a case study in coal mines of Eastern Alborz and Tazareh big mine, failure data and production pauses for seven months have been used to model and analyze the machinery reliability. The subsystems, comprising compressed air production, ventilation of mine network, excavation and extraction of coal, have 100% reliability, and modeling and analysis of reliability are only carried out for mine transportation navy. After collection and classification of failure data, relating to transportation navy equipments, the calculations of reliability were done by statistical analysis. The results showed that failure behavior of locomotive 1, conveyor belt 1, and locomotive 3 follow Weibull 2 parameter, conveyor belt 2, locomotive 2, and locomotive 5 follow Weibull 3 parameter, Vinch 1600 follow Lognormal and locomotive 4 follow generalized Gamma distribution. In the next stage, with regard to the statistical analysis and considering series combination for machines in each transportation route reliability of each route was calculated. Having considered the parallel combination of routes, reliability of the mine transportation navy was calculated. The result showed that the reliability of transportation navy reduced to zero after 180 hours, to 80% after 43 hours, and to 50% after 64 hours. Finally, by using results obtained from reliability analysis, a preventive maintenance plan baxsed on reliability to improve performance of transportation navy in Tazreh big mine was proposed. According to this plan, the reliability changes between 97% and 100%.