Abstract: To clarify the shock wave structure and its evolution of turbine cascades working in two different conditions, constrictive and contrictive-expandable, the blade surface Mach number distribution and Mach contours were obtained with numerical simulation. With the simulation result analysis, the law of shock wave evolution, and the main difference between the shock wave structures of constrictive and contrictive-expandable turbine cascades in transonic working conditions were obtained. The separation standard of the boundary layer behind the shock wave was also obtained. When the pressure ratio of post and pre the shock wave reaches 1.4, the boundary layer will separate.