[Objective] To compare the incidence of C5 palsy of mixed cervical spondylosis, which was treated by posterior open-door laminoplasty combined with decompression of intervertebral foramen and posterior open-door laminoplasty alone. [Methods] From January 2015 to June 2019, a total of 68 patients with mixed cervical spondylosis were included in this study. Among them, 38 patients underwent posterior laminoplasty (simple laminoplasty group), 30 patients underwent posterior laminoplasty combined with selective decompression of intervertebral foramen (combined group). VAS was used to evaluate the improvement of neck and upper limb pain, JOA score was used to evaluate the improvement of function. The operative time, blood loss and incidence rate of C5 palsy were recorded. [Results] There was no significant difference in age, gender and intraoperative blood loss between the two groups. The operation time of the combined group was significantly longer than that of the simple laminoplasty group. There was no statistical difference in the VAS and JOA scores of neck pain pre- and post-operation. The VAS score of upper limb pain was better than that of the simple laminoplasty group, and the incidence of postoperative axial pain and C5 palsy was significantly lower than that of the simple laminoplasty group. [Conclusion] Posterior laminoplasty combined with foraminotomy can effectively reduce the incidence of C5 palsy.