Abstract: Near-infrared (NIR) spectroscopy combined with net analyte signal (NAS) processing were used to evaluate the uniformity of tobacco casing. The NIR spectra from processed tobacco samples with casings were orthogonally projected into the spectral space spanned by the samples without casing to obtain the NAS of the casing. The similarity between the samples with and without casings was then evaluated by calculating the norm of the obtained NAS. The results showed that: 1) The NAS norm was positively correlated with the mass fraction of the casing applied. 2) By on-line measurement of NIR spectra of tobacco samples with casings in the production line, the NAS norm of each processed tobacco sample and its corresponding coefficient of variation were calculated. The casing uniformity coefficient obtained had the same trend as that measured by the standard industrial method. The NAS analysis method based on NIR spectra was easy to operate and efficient, and it could be used in the rapid evaluation of tobacco casing uniformity. 3) The use of NAS analysis method to evaluate the casing uniformity of tobacco samples under different spacer sleeve and valve core positions could achieve the optimization of the spacer sleeve and valve core position of the spraying nozzle in the casing machine.