Accurate implantation of pedicle screw（ PS） is very important in spinal surgery. Developing new realtime intraoperative monitoring and navigation methods is an important research direction. Near infrared spectroscopy test system is used to collect the spectra of fresh porcine vertebrae

bovine vertebrae and ovine vertebrae

reflectance spectra of the test points along the PS implantation path are obtained

so as to research on characteristic difference of near infrared of different animal vertebrae. Then a method for calculating the optimal slope factor is proposed

which is compared to the spectral area factor

peak factor and specific slope factor proposed in previous studies. The results show that the optimal slope factor is more accurate and robust for distinguishing different vertebral tissues. This factor can be used as the optimal recognition factor

which is applied in analysis and research on vertebral tissues of different animals along PS implantation path.