Objective To investigate the perioperative risk factors for CO₂ retention during high-frequency jet ventilation (HFJV) in patients undergoing suspension laryngoscopic surgery, and to analyze the relationship between CO₂ retention and body mass index (BMI). Methods Fifty-nine patients with ASA Ⅰ or Ⅱ undergoing suspension laryngoscopic surgery were inserted transnasally with a jet catheter modified from a suction tube, and the head of jet catheter was connected to the machine of HFJV. Jet ventilation was executed with the frequency of 60 beats per min, the pressure of 2 kPa/kg and I:E=1:(2.0-2.5). Anesthesia was induced by fentanyl, propofol and succinylcholine, and was maintained by intermittent injection of propofol and succinylcholine. Heart rate (HR), mean artery pressure (MAP), SpO₂ and blood gas analysis were recorded at a series of time points including the timepoint before anesthesia (T₀), during the intubation (T₁), laryngoscope suspending (T₂), 10 min after the beginning of jet ventilation (T₃), during the extubation (T₄) and 10 min after the extubation (T₅). Perioperative medication and other relative conditions were also recorded. Results It was identified that sex, body weight and height strongly correlated with CO₂ retention during operation in adults by Logistic regression analysis. The risk of CO₂ retention decreased significantly in females compared with males, and the former was as 7% as the later. As height increased by 1 cm, the risk of CO₂ retention reduced to 77%, while as body weight increased by 1 kg, the risk of CO₂ retention increased to 116%. The BMI of population with CO₂ retention was higher than that without CO₂ retention. The BMI over 25.224 could be considered as the most important risk factor correlated to the occurrence of CO₂ retention. Conclusions The higher BMI could be regarded as the risk factor of CO₂ retention during HFJV in adults.