Objective To investigate the effect of different ranges of facet joint resection on the stability of cervical spine, and to provide a biomechanical theoretical basis for clinical surgery. Methods A normal finite element model of the cervical spine C5-6 was established based on the CT data, and different ranges (0, 25%, 50%, 75%, 100%) of unilateral facetectomy and laminectomy models were obtained by simulating cervical endoscopic surgical operations. Comparing the ROM of C5-6 and von Mises stresses of the discs in each group. Results Except for flexion, M1 and M2 show insignificant changes in ROM and disc von Mises stresses in each direction compared with M0. M3 shows an obvious increase in ROM and disc von Mises stresses in each direction compared with M0, the ROM increases by 27%, 4%, 3%, 13%, 5%, 16%, and von Mises stress increases by 32%, 4%, 2%, 5%, 9%, 5%, respectively. M4 and M5 show a significant increase in ROM and disc von Mises stresses in each direction compared with M0. For the M4 model, ROM increases by 27%, 14%, 6%, 24%, 7%, 167%, and von Mises stress increases by 33%, 13%, 3%, 32%, 10%, 130%. As for the M5 model, ROM increases by 27%, 17%, 6%, 25%, 7%, 167%, and von Mises stress increases by 33%, 29%, 8%, 33%, 12%, 138%. Conclusions As the range of unilateral facetectomy increased, the ROM and extreme values of disc von Mises stresses in cervical segments gradually increased. the cervical spine shows significant changes in ROM and disc von Mises stresses when the facet joint resection on one side exceeded 1/2. More than 1/2 of the facet joint should be preserved in surgery to avoid medical instability.