For the sake of CFD simulation on the turbine flow field and practical manufacturing, the 3-D modeling of bent-elbow draft tube was analyzed, which showed that the common methods have a fussy process, not easy to modify and smooth. Therefore, this paper proposed a new method that overcomes the defect of the common method, has simple process, generates smooth surface, modifies flexible, and has a large adaptability. So the design intent can be more accurately realize through this method. Validated by instance and CFD analysis, the design method of draft tube agrees with the requirement of design assumption, and the flow of the draft tube are smooth and good.