The process from test starting to supersonic flow state established in an outlet-opening wind tunnel, i.e. the starting problem of supersonic flow, has become a recognized challenge. The aim is to establish feasible flow field starting method, laying the foundation for the use of outlet-opening wind tunnel. Three-dimensional numerical research on starting problem of supersonic compressor cascade was carried out in the supersonic wind tunnel at Shenyang Engine Research Institute. The failure reason of supersonic flow field starting on experimental condition was analyzed, three flow field starting schemes were established. The results show that: The starting failure reason is the formation of a strong normal shock wave at the leading edge of the cascade. Increasing the inlet total pressure alone cannot establish the supersonic flow; The supersonic cascade flow field can be started by increasing the overflow gap width on lower wall side, but the number of effective cascade passages decreases and the boundary layer thickness increases; Maintaining the width of overflow gap on the upper and lower walls at more than 1.0 pitch, setting upper and lower supersonic walls in front of cascade and conducting suction can effectively start the supersonic flow field. The maximum fluctuation of outlet Mach number is 0.01, the maximum fluctuation of outlet flow angle is 0.09°. The periodicity can meet the experimental requirements.