Objective：To assess the changes of ocular parameters and to evaluate the therapeutic effect after pulse treatment of glucocorticoid in patients with thyroid-associated ophthalmopathy（TAO） based on quantitative ocular muscle structure measurement of MRI. Methods：Eighteen TAO patients were enrolled for 3.0 T MRI orbit scan before and after methylprednisolone treatment. Quantitative measurement of orbital structures including exophthalmos values，fatty tissue thickness of inner side in eye balls，thickness of extraocular muscles with maximum signal intensity and signal intensity ratios（SIR）of extraocular muscles to ipsilateral temporal muscles were compared before and after treatment. Paired t test was used to compare changes of parameters before and after methylprednisolone pulse treatment. Results：After treatment of classical methylprednisolone，exophthalmos values and fatty tissue thickness of inner side in eye balls didin’t obviously changed，while SIR of extraocular muscles to ipsilateral temporal muscles，thickness of extraocular muscles with maximum signal intensity and CAS score decreased significantly. Conclusion：Glucocorticoid therapy can reduce SIR of extraocular muscles to ipsilateral temporal muscles，thickness of extraocular muscles with maximum signal intensity in TAO patients. MRI quantitative ocular muscle measurement can evaluate glucocorticoid treatment on TAO.