Abstract: In order to study optimal operating cost and its variation rules of compressor stations, an optimal operating cost calculation software is programmed for a compressor station on the basis of BWRS equation. In this software, the enumeration method is used to calculate successively the operating costs of all compressors with different distributions under a fixed operating condition. Then, the optimal operation cost under the fixed operating condition is confirmed for the compressor station after all the calculated costs are compared. In this paper, taking the compressor station (the initial station) in an existing pipeline network as an example, the software is used to calculate its optimal operating cost in different working conditions (incoming gas pressure from the source, intake pressure (the outlet pressure of reciprocating compressor) of downstream pipelines and total gas volume from the source), so as to identify its variation rules. It is indicated that the intake pressure of downstream medium pressure pipelines is a critical value. When the incoming gas pressure is not lower than the critical value, the optimal operating cost will decrease remarkably. Through the analysis, the medium pressure pipelines are at full output state while the optimal operating cost is realized in this station, having no relation with the change of boundary conditions.