Objective To assess the value of the whole spine scanography with supine position under traction and the whole spine scanography with erect position in guiding the preoperative surgical plan for patients with moderate to severe scoliosis by comparing and analyzing the data of the 2 methods. Methods Patients with moderate to severe scoliosis who visited The Second Affiliated Hospital of Naval Medical University (Second Military Medical University) from Jan. to Dec. 2021 and had weight-bearing supine whole spine positive and lateral radiographs under traction were retrospectively selected, and a total of 82 patients were included after screening by inclusion criteria. The patients’ age, gender, preoperative erect position, weight-bearing supine position under traction and postoperative erect position whole spine Cobb angles, surgical options, postoperative Cobb angle correction rate and spinal flexibility were analyzed. The patients were divided into groups with spinal flexibility≥30% and spinal flexibility＜30%, and the relationships between spinal flexibility and postoperative correction rate, as well as the selection of orthopedic surgery options, were analyzed. Results Among the 82 patients, 57 were female and 25 were male, aged from 6 to 63 years, with an average age of (23.0±14.3) years. The preoperative Cobb angle was (69.90±27.74)°, the Cobb angle was (42.33±30.31)°under traction, postoperative Cobb angle was (13.53±14.87)°, and postoperative Cobb angle correction rate was (80.90±17.36) %. The postoperative Cobb angle correction rate in the group with spinal flexibility≥30% was higher than that in the group with spinal flexibility＜30% (［86.97±15.39］% vs ［74.41±17.74］%; t＝2.802, P＝0.011). The proportions of patients in the spinal flexibility≥30% and ＜30% groups receiving osteotomy and orthopedic surgery were 61.0% (25/41) and 80.5% (33/41), respectively (χ²＝3.770, P＝0.052). Conclusion For patients with moderate to severe scoliosis, preoperative weight-bearing whole spine scanography with supine position under traction and whole spine scanography with erect position can provide data such as spinal flexibility and Cobb angle for the selection of surgical options.