Orbital venous varix is an uncommon venous malformation of the orbit, divided into primary and secondary types. Orbital varix most commonly involves the superior ophthalmic vein and is rarely complicated by thrombosis. We report a case of inferior ophthalmic vein varix complicated by acute thrombosis, who presented with acute visual loss and proptosis. Lateral cantholysis was performed and high-dose steroid was given to relieve the patient’s symptoms. The thrombus of the orbital varix gradually regressed in 1 month and completely resolved in 6 months.