Scanning Beam Interference Lithography (SBIL) is an effective way to fabricate monomeric large-area high-precision gratings. Using dual-frequency laser interferometer feedback table position to splice interference fringes accurately, the measurement error will inevitably introduce grating engraving error and reduce the diffraction wavefront quality of grating. The intrinsic error caused by the laser interferometer’s structure was analyzed, and the evaluation method of the intrinsic error index of the laser interferometer in complex environments was proposed. The theoretical models of dead path error and measuring optical path variation error combined with actual working conditions and empirical formulas were established. The coupling relationship between rotation and displacement of any table point was deduced by constructing translation and rotation operators, and the measurement errors under different table attitude roll angles were simulated. The displacement error experiment and grating scanning exposure experiment were carried out. The experimental results show that the displacement error is consistent with the theoretical calculation results. The diffraction wavefront of the 200 mm×200 mm grating is 0.278λ@632.8 nm. The analytical method in this paper connects the transmission link between the grating diffraction wavefront and the measurement error, laying a theoretical and experimental foundation for the fabrication of meter-size nano-precision holographic gratings.