Abstract: A small dimension two stage transonic axial compressor has been designed with blade tip veloicty 436m/s and design revolution 45000r/min.Its tests has been carried out to investigate the performance of this compressor.It is shown that its performance attains or exceeds its design specifications.This paper also considers the effects of radial and axial clearances,probe blockage,step matching and measuring techniques on the performance of the compressor.