A 50-year-old man with Marfan syndrome, was given a diagnosis of pseudoaneurysm in an anastomotic site of the left coronary artery after Bentall operation, with severe calcification. He was successfully treated with reanastomosis of a new graft to the left main trunk by the removal of a calcified intima. Coronary artery bypass grafting was not possible because his coronary arteries were covered with thickened fatty tissue due to a previous omental flap procedure for mediastinitis, and therefore we chose left main trunk coronary angioplasty. The whole calcified intima was excluded with a dissector and resected at both ostias of the left descending artery and left circumflex artery. An 8-mm woven Dacron graft was anastomosed at the left main trunk by large stitches of adhesive tissue around the adventitia, to the inside of the lumen of the left main trunk. The patency of the left main trunk was confirmed by CT and he was discharged in a good condition. Close observation is needed for long-term morbidity.