Implants are used in operative reconstruction of bony defect in case of blow-out fracture. If there is a large bony defect, the thin and flexible implants can not sustain intraorbital pressure, so it may be displaced. To prevent postoperative displacement of the implant, we tried reinforcing the center of the implant, where the intraorbital pressure was focused, piling up two pieces of porous polyethylene Implants(Medpor(R)) cross- shaped. 190 patients of large blow out fracture were divided into control group(n=95) who received classic orbital wall reconstruction and study group(n=95) to whom we inserted two small pieces of Medpor(R) one by one and covered a large defect cross shaped. We compared two groups in operative time, duration of postoperative accommodation and re-operation number. Operative time was assessed as shorter in study group(16.73+/-4.24min vs 21.40+/-5.32min, p> or =0.01). Duaration of postoperative accommodation also assessed as shorter in study group (2.05+/-0.70 weeks vs 3.00+/-1.00 weeks, p> or =0.01). There was no specific difference between two groups for re- operation number (3 vs 3, p=1.00). The method to insert two small pieces of Medpor(R) one by one and covered a large defect cross shaped shows shorter operative time and duration of postoperative accommodation than the classic method inserting large one piece of Medpor(R).