Objective To explore the value of color doppler ultrasound in infants with hypothyroidism between 0 to 3 years old before and after treatment .Methods The normal infants ,whose thyroids were examined by two‐dimensional ultrasound and were used by color doppler ultrasound ,were used as control group .The clinically diagnosed infants with transient hyperthyroidism or permanent hyperthyroidism were used as experimental group .The thyroids were examined by multiple ultrasonography before and after the treatment respectively in different periods .The measured values of thyroids were compared each other .Results In in‐fants with transient hyperthyroidism ,the major ultrasonographic findings were atrophy of thyroids before the treatment .Most of these thyroids enlarged ,and a small part of them recovered after the treatment .In infants with permanent hyperthyroidism ,the pri‐mary finding was thyroid agenesis ,and followed by atrophied before the treatment .The thyroid agenesis exist in most cases and few cases recover with normal values after the treatment .Conclusion Color doppler ultrasound can indirectly reflect the thyroid devel‐opment situation in infants .Combined with the advantages of non traumatic and high repeatability ,it can be used as an important auxiliary examination method for clinical diagnosis of hypothyroidism in infants .