Echelle grating is used extensively in spectral instruments owing to its advantages, such as the advanced intrinsic dispersion and resolving power. But while ruling the echelle grating, there may be some periodic components of spacing errors which will seriously affect the performance of grating diffraction and lead to defects of the diffraction effects. In response to this situation, the effect of grating’s line error on diffraction spectrum, diffraction order, wavefront error, the intensity of the rowland ghost line and the intensity of stray light was proposed. What’s more, a method for analyzing the grating’s line error from the aspect of the diffraction efficiency was proposed. Under certain conditions, the ruling errors for meeting every kind of requests are 1 265.8 nm, 352 nm, 37 nm, 112 nm, 3.4 nm respectively, which provides a direct and important reference for the ruling accuracy before ruling an echelle grating.