A mathematic model based on influence function method was established and the plan view pattern evolution rules of plates during angular rolling were studied by simulation and experimental methods. Results show that the difference in the elongation between the area near the angular point and other parts of the plate increases with the increase in the rotation angle of the first pass, which is the main reason why the length-width angle shows a downward trend with the increase in the rotation angle of the first pass. The length-width angle shows an upward trend with the increase in the rotation angle of the second pass, which can be attributed to the fact that the difference in the elongation between the area near the angular point (obtuse angle) and other parts of the plate increases with the increase in the rotation angle of the second pass. ε_w (the deformation in the width direction) increases with the increase in the rotation angle of the first or second pass, which is the primary reason why the width spread increases with the increase in the rotation angle of the first or second pass. Considering the same absolute reduction amount of the two passes, when the rotation angle of the second pass is two times the rotation angle of the first pass, the plates can return to almost rectangular. The predicted length-width angle and width spread values are in good agreement with the experimental ones, indicating that the established computational model based on influence function method can accurately estimate the length-width angle and width spread.