Abstract: The apparent straight strip that has “potential” shape defects will yield various warping deformations after a shearing process. The generation mechanism and deformation behavior of this warping are studied. According to the bending theory of a large deflection and the principle of minimum potential energy, the spline finite element method (spline FEM) of nonlinear buckling is established. Under center wave’s, edge wave’s, quarter wave’s and composite wave’s critical residual plastic strain, the warping deformation of a shearing process is simulated and analyzed. The simulation results show that: the basic reason of warping for shearing is that the uneven distribution of vertical extension in the width direction caused by small-size-strip overall-buckling. The warping value is decided by the longitudinal plastic strain differential, and the greater of the plastic strain differential, the bigger of the warping value. For equal shearing, each of the plastic strain has a critical number of shearing, when the number of shearing is greater than the critical number, a small size strip will be kept straight.