Abstract: In order to explore the influence of crimping dimension of self-locking nut on the locking performance, and obtain the best crimping dimension when the inlay nut reaches the maximum tightening torque in the standard, for the inlay nut for aviation composite sandwich structure, the FEA-based tightening amount is developed. The finite element analysis of the effect of tight torque and statistical theoretical data. This article explains the structure and working principle of the insert, completes the establishment of the model, the division of the mesh, the setting of boundary conditions and loads, and the finite element simulation. The results show that: with the increase of the crimping dimension, the locking torque gradually increases. The best crimping dimension of the M4 insert made of 30CrMnSiA is 0.2 mm, and the maximum locking torque is 1.55 N · m; M5 and M6 inserts are the best. The optimal closing volume is 0.22 mm, and the maximum tightening torque is 2.1 N · m and 3.1 N · m respectively.