In the study of narrow linewidth laser light echol detection under strong background, we utilize spectral filtering method to filter out background light and improve the signal-to-noise ratio. For the grating filter system, the transmission of signal light through the atmospheric channel will cause the wavefront phase distortion, and this will have a certain effect on the filtering performance of the system, so it is necessary to study it further. Aiming at the application of grating spectral filtering in the laser atmospheric transmission detection direction, based on the laser atmospheric transmission theory and the grating diffraction principle, we establish the simulation model of the spectral intensity distribution of the grating when the incident light field is atmospheric disturbance light field. The influences of atmospheric coherent length and system structural parameters on system performance are analyzed. The system of the grating spectral filtering technology and the atmospheric applicable conditions are given. When the atmospheric coherent length r0 is greater than 0.05 m, sub-nanometer level spectral filter linewidth (full width at half maximum is 0.3 nm) is obtained, and the transmission of the effective spectrum exceeds 0.90. The results are verified by a large number of simulation experiments.