Abstract: Based on three-dimensional Hashin failure criterion, and quadratic nominal stress criterion and BK failure criterion of the bilinear Cohesive damage model, the delamination damage of carbon fiber reinforced plastic unidirectional plate during drilling was simulated by VUMAT subroutine in ABAQUS/Explicit module, and the simulation results were verified by the ultrasonic C scan results after drilling. The effect of diameter and vertex angle of twist drill on delamination damage was studied. The results show that the tested maximum damage diameter of damage area of unitirectional plate after drilling was 25.6 mm, and the delamination factor was 2.56; the maximum damage diameter was 25 mm, and the delamination factor was 2.50 by finite element simulation. The relative error between experimental results and simulation results was only 2.4%, proving the accuracy of the finite element model. Compared with the top surface layer interface and intermediate interface, the delamination factor of the lower surface layer interface of unidirectional plate was the largest, and the delamination damage was the severest. The delamination factor increased with the increase of diameter and vertex angle of twist drill, and the delamination damage degree also increased.