Abstract: A strong swirling structure exists in the high-pressure stage turbine under non-design conditions,which affects the low-pressure stage turbine performance. This deterioration effect has a strong correlation with the swirling pattern,while existing researches have not covered the variation mechanism of the turbine outlet swirling at different operating conditions. In this study,the evolution law of the swirling flow on the high-pressure stage turbine was investigated experimentally using an independently designed X-type two-dimensional isothermal hot-wire stepper structure. Results demonstrate that turbine outlet swirling patterns are strongly dependent on the expansion ratio and speed. Swirling intensity exhibits a non-monotonic trend as the speed increases,with the swirling direction reversal occurring at an expansion ratio of 1.1 and a speed ratio of 0.1. Moreover,the axial and circumferential velocities of the swirling have a strong coupling relationship,with increases in swirling intensity and circumferential velocity leading to Wake-like characteristics in axial velocity distribution. Under pulsating inflow conditions,velocity fluctuations at the turbine outlet depend on pulsating inflow frequency,with axial velocity gradually increased by up to 5% and little change in circumferential velocity.