Abstract: The reliable operation of cyclone separators is quite significant for the stable gas supply of pipelines. So far, however, there is not any method available for the operation reliability evaluation of cyclone separators. In high pressure systems, the operation reliability is associated with the structure reliability. Based on existing research, however, this relation has not been understood sufficiently. In this paper, a method which can be used to evaluate the operation reliability of cyclone separators was worked out by virtue of structure reliability analysis and Markov process of maintainable systems, together with practical engineering experience. Based on this method, the operation reliability of a certain type of cyclone separators used in the West-to-East Gas Pipeline was evaluated on the basis of the actual structure and operation parameters. Based on the evaluation results, the feasibility of this method is confirmed. It provides a reference for the operation reliability evaluation of similar equipments.