Using R245FA as working fluid, FLUENT as computational fluid dynamics (CFD) software and standard K-Ε model, the number of blades was 15,17,19,21,23,25,27, and the blade mounting angles were 24 ° , 28 ° , 32 ° , and 36 ° , respectively, a 40 ° cascade is numerically investigated. The calculated results show that when the number of blades is 21 and the angle of installation is 28 ° , the circumferential average velocity, the outlet average temperature and the velocity coefficient of the guide cascade are greatly improved compared with the original design. Under the number of blades and the angle of installation, the blade height is obtained by linear fitting. The results show that the flow conditions in the optimized flow passage are good, which provides a reference for the design of highly efficient guide cascade.