The adjustment of the parallel plate dual-path lateral-shearing interferometer was investigated and a method to correct the angle error of the parallel plate was proposed. The wavefront of the laser is fitted with the Zernike polynomial. Based on theoretical derivation, it is found that the difference between oblique astigmatism of wavefront in two directions has a linear relationship with the angle error of the parallel plate. Therefore, the difference between oblique astigmatism of wavefront in two directions can be used as a feedback to adjust the angle error of the parallel plate. The angle error of two parallel plates can approach zero by making the difference between oblique astigmatism of wavefront in two directions is equal to zero during adjusting the parallel plate lateral-shearing interferometer. The linear relationship was further proved by experiments. When defocus aberration is -3.224 7±0.001 8 and the fluctuation range of the difference between oblique astigmatism of wavefront in two directionsis±2.0×10^-3, the experimental angle error of two parallel plates for our experimental system can be controlled within 8.82″.The effect of higher-order aberrations on the accuracy of angle error adjustment is approximately 1.63″.This method has the advantages of easy adjustment, high accuracy, and easy process operation.