To define the value of 20MHz high frequency B mode ultrasound in extraocular muscles disease. METHODS:10MHz and 20MHz B-mode ultrasound were used to observe the extraocular muscles on normal persons and different extraocular muscle diseases from Jan 2011 to Dec 2011. RESULTS:In the normal eyes and strabismus patients, 20MHz high frequency ultrasound could clearly show the morphological characteristics of the extraocular muscles. Symmetric extraocular muscle thickness was not significantly different in normal eyes. Compared with 10MHz ultrasound, its measured value was significantly increased. Different extraocular muscle diseases had different performance. CONCLUSION:20MHz high frequency ultrasound is suitable for observing extraocular muscles of the normal eyes and strabismus patients. The display is better than 10MHz ultrasound. But there are certain limitations in the types of extraocular muscle disease with extraocular muscle thickness increase.