Abstract: A stationary calculation method was proposed for calculating multicomponent square cascades with additional flows. The method is based on the quasi-linearization of cascade governing equations. A successive approximation of the cascade separation factor was used to accelerate the convergence process. Numerical calculations indicate that the results obtained by using the stationary method and transient method are consistent, however the stationary method can reduce computational time substantially compared with the transient one, and so it is suitable for calculating square cascades with additional flows or more complex cascades such as square-off cascade.