Objective To determine localization of the rat thyroid gland by ultrasound technology, analyze and evaluate lesions and the degree of modeling in the rat nodular goiter model, and provide a technical method for diagnostic evaluation of the rat model of nodular goiter and related thyroid diseases. Methods Forty 6 ~ 8 weeks old SPF-grade Wistar rats (male and female) were used as the control group and 20 rats were instilled with a propylthiouracil (PTU) solution for 8 weeks to establish a rat model of nodular goiter. Ultrasound examination of the thyroid gland was performed after modeling, along with pathological examination for comparison with ultrasound. Results Ultrasonography showed that the anterior-posterior and medial-lateral diameters of the thyroid gland in the model group were significantly larger than those in the control group (P<0. 001). Conversely, asymmetric enlargement of the gland was observed in the model group. The shape and size of thyroid tissue and the follicle size were irregular in HE-stained thyroid glands of the model group. In the group, epithelial cells were obviously hyperplastic, disorganized and unevenly distributed with compressed colloid. Ultrasound and pathological tests were consistent with the disease diagnosis. Conclusions Ultrasound is a good method for in vivo evaluation of a rat nodular goiter model.