Abstract: With reference to " Aircraft Engine Emissions" promulgated by the convention on International Civil Aviation,we designed an emission measuring system. Emissions of two JT3D-7 gas turbine engines were measured by means of the system on the test rig of AMECO company. The measured Emissions Index EIco,EIHC,EINOx and SN of these two engines were compared with the JT3D-7 typical EI data. The accuracy of this system is about 3%, which was much better than the ICA's requirement (10%-15%). In the analytical formulations for the EI and AFR parameters of the convention, assumptions were made that all concentration measurements were of the " wet sample". In our practice, the CO₂, CO and NO_x concentration measurements were made on a "dry" basis. So we derived the corrected formulations for EI and AFR calculations of these engines. The data of experiments were varied in a quite wide range to prove that the sampling and measurement system is acceptable in engineering.