Objective To investigate the clinical value of ultrasound features in differentiation of benign and malignant lesions in Bethesda class Ⅲ/Ⅳ/Ⅴ thyroid nodules. Methods A retrospective analysis was conducted on the clinical data of 101 patients with Bethesda class Ⅲ/Ⅳ/Ⅴ thyroid nodules who underwent ultrasound-guided fine needle aspiration cytology examination from January 2023 to June 2025. All patients underwent high-frequency ultrasound examination, and the ultrasound characteristics of nodules were recorded and statistically analyzed. Using surgical pathology as the gold standard, the patients were divided into a benign group （n=50） and a malignant group （n=51） to compare the differences in ultrasound characteristics. Multiple logistic regression was used to screen independent risk factors for malignant nodules, and stratified analysis was conducted to evaluate the predictive power of ultrasound features in different Bethesda grades. Results The proportion of single nodules, unclear boundaries, solid structures, aspect ratio>1, low echogenicity, and microcalcifications detected in the malignant group were significantly higher than those in the benign group （P<0.05）. Multiple regression analysis showed that the six ultrasound features mentioned above were independent risk factors for thyroid malignant nodules （OR=4.08-5.76, P<0.05）. Stratified analysis showed that： （1） in Bethesda class Ⅲ nodules, hypoechoic and solid structures were independent predictors of malignancy; （2） if Bethesda class Ⅳ nodules were combined with ≥ 2 high-risk ultrasound features, the risk of malignancy was greater than 80%; （3） the malignant risk of Bethesda class Ⅴ nodules exceeded 90%, and microcalcifications could assist in predicting classic papillary carcinoma subtypes. Conclusion Ultrasound features can effectively refine the malignant risk stratification of Bethesda class Ⅲ/Ⅳ/Ⅴ thyroid nodules, providing an objective basis for individualized treatment plans （such as short-term follow-up, molecular testing, or surgery） in clinical practice, helping to reduce overtreatment and improve patient prognosis.