Abstract: Gas transmission efficiency coefficient of gas pipeline expresses the degree of deviation from the ideal computational conditions for actual operation of the pipeline. Its value affects significantly actual transmission capacity of the pipeline, as well as the construction investment and operation and maintenance cost of the pipeline. In order to ensure that the pipeline can maintain its design throughput during operation under the optimal economic circumstances, it is necessary to rationally determine the gas transmission efficiency coefficient value. In this paper, taking the specific project as an example, theoretical research and comparative analysis are conducted on several common hydraulic friction computational formulas like Colebrook-White (C-W) and Panhandle-B. According to the relevant specifications in GB 50251-2003 Code for Design of Gas Transmission Pipeline Engineering on E value used in Panhandle-B friction computational formula, the rationality of taking gas transmission efficiency coefficient value as 1 in the C-W hydraulic friction computational formula used in relevant design in China now is verified. Through analytic study on the gas transmission efficiency coefficient, proper adjustments that should be made for the pipe projects with different pipe diameters, pipe wall roughness and Reynolds numbers given gas transmission efficiency coefficient value of 1 are proposed.