Abstract： Objective:To provide references for the health management of thyroid nodules in naval flying personnel by analyzing the ultrasound characteristics of naval flying personnel with thyroid nodules.Methods:A total of 306 naval flying personnel, who were diagnosed as thyroid nodules in yearly health examination in the Third Sanatorium of Air Force Healthcare Center for Special Services Hangzhou from January of 2019 to December of 2021, were selected as the research subjects. They were divided into 3 groups by age (20-29 years, 30-39 years, ≥40 years), 2 groups by flying hours (<3 000 h, ≥3 000 h) and 3 groups by aircraft types (helicopter, transporter, fighter). The characteristics of thyroid nodule ultrasound images were retrospectively analyzed and the size, quantity and classification which defined in Chinese-thyroid imaging reporting and data system (C-TIRADS) of thyroid nodule were compared among the groups of different ages, flying hours, and aircraft types.Results:Among 306 naval flying personnel with thyroid noedules, 280 cases (91.50%) were small nodules (diameter <1 cm), 26 cases (8.50%) were large nodules (diameter ≥1 cm). One hundred and fifty-one cases (49.35%) were single nodules and 155 cases (50.65%) were multiple nodules. There were 135 cases (44.12%) with C-TIRADS grade 2 thyroid nodules, 158 cases (51.63%) with C-TIRADS grade 3 nodules, and 13 cases (4.25%) with C-TIRADS grade 4 nodules. There were significant differences in the size, number, classification of composition ratio of thyroid nodules among different age groups ( χ2=8.86, 5.94, 46.20, P=0.013, 0.051,<0.001). There were significant differences in the size and classification of composition ratio of thyroid nodules between different flying hours groups ( χ2=16.91, 24.35, both P<0.001). The proportion of C-TIRADS grade 4 nodules in the flying hours ≥3 000 h group was higher than that in the <3 000 h group, with a significant difference ( χ2=4.77, P=0.029).There were no significant differences in the size, number, classification of composition ratio of thyroid nodules among different aircraft types groups (all P>0.05). Conclusions:Age and flying hours have effects on size and classification of composition ratio of thyroid nodules in flying personnel, and age also has the effect on quantity. A scientific and systematic follow-up mechanism would be helpful to assess the risk of thyroid cancer and give early warning for the timely intervention.