Objective To present the changing of the parameters of orbital volume after endoscopic transethmoid medial orbital wall decompression combined with the endoscopic transethmoid intraconal fat-removal orbital decompression in thyroid associated ophthalmopathy (TAO).Methods A retrospective chart was reviewed in 11 patients (20 eyes) receiving orbital decompression for the treatment of exophthalmos secondary to TAO from September 2014 to August 2015. All patients diagnosed TAO were in stable and inactive phase at least for 6 months. High-resolution computed tomography (HRCT) scan were performed in all patients before and 3-month after surgery. CT scan of orbit and computer-aided measurement software were used to measure the exophthalmos. Changing of the parameters of orbital volume were recorded for analysis its relationship with the amount of proptosis reduction.Results The exophthalmos was signiifcantly decreased after surgery. Medial rectus volume, fat volume and orbital volume were larger postoperatively. The changing of rectus volume and fat volume both had negative correlationship with the amount of proptosis.Conclusions The thickening of medial rectus 3-month postoperative may due to the removing of medial wall of orbit during the surgery. The stimulation of the surgery may be another reason. The changing of rectus volume and fat volume both had negative correlationship with the amount of proptosis.