Abstract: Abstract: Operation efficiency assessment is very meaningful for enhancing energy-saving and consumption-reduction level of the natural gas operating enterprises. In order to perform an operation effciency assessment on Sichuan-Chongqing Loop Natural Gas Pipeline Network, this paper bases on the analysis results of pipeline network characteristics, energy consumption structure and operation effciency evaluation particularity, establishes a 4-layer 10-index operation effciency assessment system using APH layered analysis principles, and realizes quantitative evaluation of the whole pipeline effciency by introducing a "comprehensive effciency index" into the system, which integrates the infuences of various energy consumption factors. The index system has been applied in the operation effciency assessment of main Sichuan-Chongqing Gas Loop Network in February, 2012. The results show that the operation efficiency of several compressor station in 19th Compressor Station, 1st Compressor Station, 18th Compressor Station, 2nd Compressor Station and 16th Compressor Station is lower than the mean value, and the energy consumption management of the compressor station shall be strengthened; the average comprehensive energy effciency value from 1st Compressor Station to 8th Compressor Station upstream sections, 9th Compressor Station to 20th Compressor Station middle sections and the 21st Compressor Station to 23rd Compressor Station downstream sections is respectively 0.73, 0.833 and 0.68, refecting the overall energy effciency status of the Sichuan-Chongqing Gas Pipeline Network is higher in the middle sections than in the upstream/downstream sections. It complies with the Sichuan-Chongqing Gas Pipeline Network without booster stations, and the assessment results provide an important basis to the energy efficiency management and optimum dispatch of the Sichuan-Chongqing Gas Pipeline Network.