Objective To compare the predictive value of the minimal transverse diameter of the subglottic airway (MTDSA) measured by B‑ultrasound, age formula method and height formula method for selection of enhanced cuffed tracheal tube. Methods A total of 120 children who were admitted to Department of Surgery, Suining People's Hospital from January 2021 to December 2021 and scheduled for tracheal intubation under general anesthesia were selected (7 cases were excluded due to loss to follow‑up and incomplete data, with a deletion rate of 5.83%). According to the stratified randomization method, the samples were divided into three groups: an age formula group (n=36), a height formula group (n=39) and a MTDSA group (n=38). The enhanced cuffed endotracheal tube was selected, and the three groups were pre‑evaluated by the age formula method, height formula method and MTDSA method measured by B‑ultrasound, respectively. The pre‑evaluated accuracy of the three methods was determined, using the optimal endotracheal tube type for successful intubation as the standard. The tube exchange rate, MAP and heart rate immediately after intubation and complications among the groups were compared. Results The evaluation accuracy of the first tracheal tube selection was 86.84% for the MTDSA method measured by B‑ultrasound, which was higher than 55.56% for the age formula method and 46.15% for the height formula method (P<0.05). Using the MTDSA method measured by B‑ultrasound, the tube exchange rate was 5.26%, and the tube exchange rate was 10.53%, which were lower than those of the age formula group (33.33% and 44.44%) and the height formula group (43.59% and 58.97%) (P<0.05). The incidences of hoarseness (2.63%) and laryngeal edema (0) in the MTDSA group were lower than those in the height formula group (28.21% and 20.51%) (P<0.05), there was no significant difference in complication rates between the age formula group and MTDSA group (P>0.05). Conclusions The MTDSA method measured by B‑ultrasound for selection of enhanced cuffed endotracheal tube has good accuracy of the first intubation, with a low incidence of complications.