Abstract: The effect of Reynolds number in small multistage axial flow compressors is described and illustrated by experimental data and numerical simulation for a four-stage axial flow compressor,of which total pressure ratio is 60 and polytropy efficiency is 084 at design points.The performance of this compressor is obtained at 100 percent of the rotational speed.The influence of variations in flow Reynolds number has been studied through experimental data at 85 percent of the rotational speed.Using a three-dimension calculation code,the detailed flow-field of this compressor at different Reynolds Numbers has been obtained.The results show that the thickness of boundary layer increases with decreasing Reynolds number,mean while the flow-field structure is changed,and the performance of this compressor will be worse.Combined with experimental data and numerical simulation,the performance of this compressor has been modified using a correlation.Considering the effect of Reynolds number,the performance of this compressor will be that the total pressure ratio is 622 and polytropy efficiency is 085 at design rotational speed.