Abstract: The clocking effect in the 1.5-stage compressor,which would be used in the 1.5-stage transonic compressor test rig,was investigated by computational fluid dynamics(CFD) method in this paper.The results show that:(1) The compressor efficiency is high and mixing loss is low when the stator wake is mixed with the outlet guide vane(OGV) boundary-layer fluid.(2) The compressor efficiency is low and mixing loss is high when the stator wake is mixed with the OGV main flow area fluid.(3) The highest efficiency is 0.4% higher than the lowest efficiency.(4) The inlet guide vane(IGV)-stator clocking effect can be neglected,just leading to 0.025‰ improvement of compressor efficiency.Besides,the optimal clocking position versus the stator-OGV axial clearance plot was got.