Recently, ultrasonography of the thyroid gland has proved to be a useful clinical diagnostic method. The newly developed high-resolution ultrasonography with color-Doppler flow mapping function can reveal fine details of the thyroid gland and the hemodynamic features of thyroid neoplasmas. Ultrasonography can deliver a diagnostic accuracy of over 90% in thyroid carcinoma, especially papillary carcinoma. However, in the case of follicular carcinoma, neither conventional B-mode ultrasound imaging nor aspiration biopsy cytology can deliver satisfactory results. Color-Doppler imaging examination of 212 follicular tumors has been carried out, resulting in the characteristic finding that a high-velocity pulsative blood flow penetrates the tumor in the case of follicular carcinoma, which led to new diagnostic criteria with color-Doppler examination. The differential diagnostic grading score using color-Doppler examination and FFT analysis can show a dramatic diagnostic accuracy of 81.0%, a sensitivity of 88.9% and a specificity of 74.2%. Ultrasound with the color-Doppler function can play a more important role in the differential diagnosis of thyroid tumors.