Abstract: Flow fields in a low speed large scale axial compressor were measured with and without pylon in design condition and near stall condition.The 2 D calculations showed good agreement with the experiment results.The measurement and calculation results show that the flow circumferential non uniformity caused by the pylon is the main reason influencing the efficiency and stall margin.2 D numerical simulation for restaggered vane has been performed,and preliminary results indicate that proper restaggering of vane can reduce the effect of pylon on the flow field.