Abstract: Additional drag (inlet/outflow momentum drag) is an important part of the engine thrust on the test bench.It is very significant for improving the precision of the engine test thrust so that the additional drag is accurately measured.This paper introduces the gross thrust and contrast calibration of test facility.At the same time,this paper studies the method of correction of additional drag which takes place during engine tsting on outdoor test stand,ground test bed and altitude test facility.Lastly,this paper gives the results of comparison testing between two altitude test facilities (Muscovite and Chinese),also gives the results of comparison testing between that of altitude test facility and ground test bed.