In order to precisely control the direction of laser beams, we analyze the error caused by the grating tilt in the system based on the optical beam pointing algorithm of the dual liquid crystal polarization grating system. Firstly, a ray tracing method based on the diffraction grating equation is used to solve the outgoing beam pointing, introducing the incident beam pointing and grating tilt angle. The correctness and accuracy of this method are verified through comparison with simulation results. Secondly, by analyzing different cases of grating tilt, we provide expressions of the grating attitude under different tilt conditions, and in combination with the ray tracing method, obtain the expressions for the outgoing beam pointing for corresponding situations, analyzing the zeroing error and rotation error caused by grating tilt. The research results indicate that within the 0° to 0.3° grating tilt angle range, the zeroing errors are within 0.25 mrad and 2 mrad respectively, and the rotation errors are around 85 mrad and 430 mrad, respectively. We propose a method for accurately calculating the pointing direction and grating tilt errors in the exit beam of a dual liquid crystal polarization grating system.