Abstract: The altitude effect on aero-engine ground test performance was analyzed in brief,and the advantages-disadvantages of the two methods used for the analysis of this effect were compared.A method was put forward to study the above-mentioned influence through the inlet pressure’s influence on the engine performance at constant ram ratio with the help of the ATF particular advantage of pressure regulation and control.The test result of an engine shows that its corrected performances agree well with the test results when the inlet total pressure is kept in the range from 70 through 90kPa and the fan corrected rotating speed,94.5% to 96.5% at a constant ram pressure ratio of 1.6.It means that engine Reynolds Number is already higher than the critical Reynolds Number when the ambient pressure is above 70 kPa or the altitude is below 3 km.In this range,the influence of the ambient pressure change on the engine corrected performance can be neglected.Thereby,engine performance at static standard sea level atmospheric condition can be determined through engine ground test with altitude less than 3 km.