Neutral detergent fiber (NDF) and acid detergent fiber (ADF) are key indices of crop-straw feeding quality. To obtain stable spectral regions for low-cost instruments, a characteristic-wavelength selection strategy based on consensus across multiple modeling workflows was developed. A total of 350 straw samples were used for calibration, and 100 independent samples were used for external validation. Spectra from 10000cm?1 to 4000cm?1 were represented as raw, standard normal variate, or Savitzky–Golay first-derivative spectra and were paired with CARS, MC–UVE, SPA, siPLS, and VIP. Partial least-squares models were repeatedly constructed under 100 Monte Carlo splits, and recurrent selections across workflows were summarized as consensus bands. The ADF and NDF target-consensus sets contained 449 and 434 variables, accounting for 14.96% and 14.46% of all variables, respectively. On the independent validation set, fixed consensus-band models produced RMSE, R2, RPD, and bias values of 13.54g/kg, 0.892, 3.05, and 1.92g/kg for ADF and 17.05g/kg, 0.890, 3.03, and -4.26g/kg for NDF. Shared bands mainly represented cell-wall information related to polysaccharide hydroxyl groups, bound water, and C—H/ C—O combination bands. ADF-specific bands supplemented celluloseand lignin-enriched responses, whereas NDF-specific bands reflected hemicellulose and bound-water status. The strategy retained stable predictive information with markedly fewer variables and provided candidate regions for compact near-infrared instruments.