Abstract: Gas trunk line is the important strategic energy channel in China. Therefore, the reliability research is essential. Through coalescing related Chinese and foreign literatures, key reliability evaluation indexes are screened, and the calculation method is provided combining with the technological characteristics of gas trunk line. A reliability evaluation method for pipe unit and compressor station unit is proposed by using basic theory of reliability and basic method of statistics. The connection between the units and system is established by using the reliability block diagram and the weak link in the system is determined through fault tree analysis. Ultimately, a reliability evaluation method for main gas pipeline is put forward.