Abstract: Aiming at disadvantages of existing multistage turbine design, such as a complicated process, long cycle, and strong reliance on experience, a one-dimensional optimization design method suitable for the three-dimensional flow channel of multistage turbine blades was proposed based on flow conservation, a real gas model, and a one-dimensional loss model, using an interior-point algorithm and a blade profile parameterization technique. A corresponding automatic optimization design platform was also developed. The blade channel was divided into several subchannels along the radial direction, and iterative optimization was performed by combining three-dimensional numerical simulation with a modified loss model. By this approach, the quasi-three-dimensional design phase was bypassed, and the number of iterations needed for full three-dimensional design was significantly reduced. Consequently, accurate design results with excellent aerodynamic performance were obtained, while both design time and dependence on prior experience were diminished. Verification was carried out using a 300 MW F-class gas turbine with four turbine stages. The results show that the turbine design obtained with this method is in good agreement with the three-dimensional numerical simulation results. Compared with the prototype design, the angle-of-attack matching between stator and rotor blades in each stage is improved, blade twist is reduced, and secondary flow loss is significantly decreased. As a result, the circumferential efficiency increases by 0.66%, the flow rate rises by 1.24%, and the shaft power improves by 1.99%.