In order to solve the problems of inconsistent closing amount and tooth outward rotation in the closing forming of self-locking nuts at large-size and small-aspect-ratio shaft-end of superalloy for aero-engine， the structure and process parameters of the closing die were optimized. For a certain type of shaft-end self-locking nut for superalloy GH2132， three kinds of taper angles for closing die were preliminarily selected according to production experience， and the optimal taper angle was determined by numerical simulation based on the maximum equivalent stress and closing accuracy. Two groups of process parameter combinations were obtained by using orthogonal experimental method and Vague set optimization method， and the optimal parameter combination was selected by comparing simulation experiments and based on the maximum damage value and maximum forming load. Finally，the simulation experiments and production validation were conducted. The results show that the problems of inconsistent closing and tooth outward rotation for this type of self-locking nut are effectively solved when the closing die taper angle is 30°， the holding time is 0.5 s， the pressing speed is 40 mm·s-1， and the friction coefficient is 0.1. Thus， this research provides a reference for the process optimization of other types of self-locking nuts.