Abstract: Bladegen software is used to parameterize the solid twisted blade, and Turbogrid software is used to complete the accurate modeling and meshing of the complex twisted blade single.  The final stage of the nuclear wet steam turbine in variable volume flow condition were calculated and analyzed by CFX software. The results show that the flow stability in the final stage of the wet steam turbine gradually decreases as the relative volume flow decreases. Steam flowing in the stage exhibits extremely complex rules, and in the 70%~85% leaf of height area, the flow field is the biggest and the stability is the worst. The research conclusion provides a reference for the future optimization of the structure and the blade shape of the steam turbine, and further improves the stage flow capacity.