Objective. The aim of this study is to explore the clinical application value of high-frequency ultrasound combined with detection of serum high mobility group box (HMGB-1), soluble IL-2 receptor (SIL-2R), and thyroglobulin antibody (TgAb) in diagnosing thyroid cancer. Methods. By means of retrospective study, 50 thyroid cancer patients treated in our hospital from January 2019 to January 2021 were selected as the thyroid cancer group, 50 patients with benign thyroid lesions were included in the benign lesion group, and 50 healthy individuals examined in our hospital in the same period were included in the control group. All study objects received high-frequency ultrasound examination, and at the same time, their serum HMGB-1, SIL-2R, and TgAb levels were measured. After that, the results of high-frequency ultrasound examination were analyzed, the diagnostic efficacy of different diagnosis methods was explored, and receiver operating characteristic (ROC) curves were plotted. Results. According to the results of high-frequency ultrasound examination, there were significant differences in echogenicity surrounding and inside the lesion, calcification, blood flow distribution, and blood flow parameters between the thyroid cancer group and the benign lesion group (P < 0.001); the HMGB-1, SIL-2R, and TgAb levels were statistically different among the three groups (P < 0.001), and the level values of HMGB-1, SIL-2R, and TgAb of the thyroid cancer group were, respectively, (12.26 ± 1.32) ng/ml, (108.65 ± 9.75) pmol/L, and (690.65 ± 34.47) IU/mL; the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of high-frequency ultrasound combined with detection of serum HMGB-1, SIL-2R, and TgAb were, respectively, 98.0%, 95.0%, 90.7%, and 99.0%, and AUC (95%CI) = 0.965 (0.931–0.999). Conclusion. High-frequency ultrasound combined with detection of serum HMGB-1, SIL-2R, and TgAb has a good value in diagnosing thyroid cancer, which should be promoted in practice.