Abstract: The effect of a yaw angle is important for the oblique impact of a long rod. The mechanism of perforation of a moderately thick aluminum target by a long-rod projectile at various yaw angles is investigated by a set of three-dimensional numerical simulations. Based on a finite element model, validated by the experimental results, this paper performs a set of simulations with varying velocities and yaw angles, and presents the features of projectile accelerations, the orientations of the velocity vector and bending of the rod. The effects of various velocities, the oblique angles and yaw angles on penetration resistance, the bending of the rod and ballistic trajectory offset are analyzed. The obtained results indicate that the bending of the rod is much more sensitive to a negative yaw angle than a positive one for the impact with obliquity. The bending of rod decreases with the increase of impact velocity. The whipping action on the projectile tail and the ballistic trajectory offset due to yaw become more obvious as impact velocity increases. There is a fundamental difference in the mechanism of energy loss between with and without yaw in oblique impact.`