Objective To observe the changes in the length of incisors to the carina (LIC) and the length of carina to the tip of the tracheal catheter (LCT) in ankylosing spondylitis (AS) patients with thoracolumbar kyphosis after pedicle subtraction osteotomy (PSO). Methods A total of 86 AS patients who underwent PSO were enrolled and their height, cervical range of motion (CROM), global kyphosis (GK), and chin‑brow vertical angle (CBVA) were recorded before and after surgery. Furthermore, LIC and LCT were measured via a tracheal tube in the median supine position under a fiberoptic bronchoscope (FOB) before and after surgery. Results Compared with those before surgery, all the patients presented remarkable increases in height and decreases in GK and CBVA after surgery (P<0.05). There were no statistical differences in CROM before and after surgery (P>0.05). All the patients presented increases in LIC and LCT after surgery, compared with those before surgery (P<0.05). Conclusions After PSO, AS patients present a shift in the tracheal catheter tip towards the glottis, and the insertion depth of tracheal tube may properly extend.