Slit coating technology, featuring high coating precision, fast coating speed, and wide coating window, possesses unique advantages in the preparation of micro/nano-structures and thin film materials. This paper investigates the structure of the slit coating head, incorporates actual boundary conditions and simulation parameters, and completes a fluid simulation analysis of the external flow field during the slit coating process. Through simulation results, the relationship between the chamfer shape of the shim and the coating thickness in the edge region is analyzed, revealing the influence pattern of shim chamfer shape on thickness stability. The chamfer shape of the shim affects the coating thickness, with an increase in chamfer size initially leading to an increase and then a decrease in coating thickness.