The invention relates to the technical field of 3D printing, in particular to a manufacturing method of manufacturing a variable-diameter complex inner runner structure by additive manufacturing and subtractive manufacturing of a preset base plate; the method comprises the steps of 1, model building and detaching; 2, base plate designing; 3, tool selecting; 4, machining preparation; 5, part I machining; 6, cutting processing; 7, part II machining; 8 cutting processing; 9, part III machining; ...and N, part N machining. By adopting the technical scheme, the problems in the prior art that the surface quality of the complex inner runner is poor; geometry precision is low; an inner surface cannot be machined; or the inner runner cannot be machined. The manufacturing method is of great significance to surface machining of complex fuel nozzles, hollow fan blades, special hydraulic elements or other complex components with the geometry features which are used for aviation engines.