Because of the divergence angle and linewidth effects, the filter’s transmission characteristics will change when a nonparallel beam irradiates the narrow-band filter. Especially at oblique incidence, the passband waveform of the narrow-band filter film is more likely to degenerate from rectangular to triangular, and negative phenomena such as the transmittance peak decrease appear. Although the known convolution model can simulate this variation numerically, there is no strict experimental verification for the model’s correctness and the accuracy of numerical analysis due to obstacles of preparation and measurement errors. For this verification, the corresponding errors are overcome through film optimization and measurement error correction. A high-performance 1064 nm narrow-band filter at an incident angle of 17° was fabricated by plasma-assisted reactive magnetron sputtering (PARMS). The transmission characteristics were measured by two spectrophotometers, Cary 7000 and Lambda 1050, separately. The spectra are coincident with the numerical simulation under different conditions. Therefore, the validity of the convolution model and the high accuracy of the numerical simulation are adequately justified.