The invention discloses a developing and manufacturing method of a main pump impeller of a nuclear power plant. The method includes the steps of manufacturing a scale impeller; determining the hydraulic design preliminarily after the scale impeller passes hydraulic performance experiment verification and meets requirements; and manufacturing a full-scale impeller. Developing and manufacturing of the main pump impeller of the nuclear power plant are completed after the full-scale impeller undergoes a full-flow experiment along with a main pump and the hydraulic performance meets the requirements during verification. The scale impeller and the full-scale impeller are obtained through 3D printing of metal. Compared with the prior art, the developing and manufacturing method has the advantages that the development cycle of the impeller can be greatly shortened through a manufacturing method of an experimental impeller for hydraulic performance verification of the main pump of the nuclear power plant, the quality of the impeller can be improved, and the application prospects are wide.