Abstract: The effects of CO₂ mass fraction, cascade inlet temperature, and outlet back pressure on the condensing flow characteristics and shock wave development of a mixed-working-fluid transonic cascade were investigated. 17 sets response surface design based on a three-factor, three-level approach was constructed to evaluate the influence of each factor on the integrated entropy production rate over the cascade plane. A quadratic regression function was then developed based on the response surface results. Minimization of the entropy production rate was performed under prescribed parameter constraints to determine the optimal parameter combination. Results show that when the CO₂ mass fraction increases from 13.45% to 23.45%, the trailing-edge oblique shock strengthens, and the angle between the inner and outer trailing shocks decreases from 136° to 125°. When the inlet temperature exceeds 374.3 K, the shock waves within the flow field intensify, and the nucleation zone concentrates near the blade trailing edge. Increasing the outlet back pressure substantially reduces shock intensity in the cascade passage, shifts the inner and outer trailing shocks upward, and enlarges their included angle. The outlet back pressure plays a dominant role in entropy production, while the CO₂ mass fraction and inlet temperature have weaker effects.