Surgical management of patients with comorbid long-term myasthenia gravis (MG) is particularly challenging and MG thus represents an independent risk factor for perioperative complications. However, few studies have reported on the perioperative assessment, prevention measures, and risks in MG patients undergoing major surgery, especially for anterior cervical spine surgery. We herein report the rare case of a 62-year-old man with a 20-year history of MG, who was admitted to our hospital with diagnosis of degenerative cervical spondylosis. He safely underwent anterior cervical corpectomy of C4, discectomy of C5-6, and fusion of C3-6. Intraoperative motor evoked potential was recorded to detect significant improvement after decompression. However, the patient suffered from progressive dysphagia, bucking, and hyperpyrexia 20 days after the initial operation. Imaging revealed titanium cage sliding and graft dislodgement. Secondary surgery was performed for posterior internal fixation from C2-7 and anterior revision from C3-6 after Halo-Vest traction, antibiotic treatment, and immunoglobulin therapy. He underwent a series of postoperative treatments, including cervicothoracolumbosacral orthosis, atomization inhalation, chest physiotherapy, antibiotics, and nutritional support. His condition improved markedly and he had no recurrence of symptoms during the 6-month follow-up. It is the rare reported case of anterior cervical spinal surgery in a patient with MG. This rare case indicates a relative contraindication to anterior-only approaches especially with multiple levels for MG patients with cervical spondylosis. Posterior approach, intraoperative monitoring, osteoporosis, postoperative strong brace protection, and supportive management should be considered for patients who were on large doses of steroids for long duration of time, given the lack of sufficient bone mineral density.