Bonnet bypass is recommended for the rare patients in whom no alternative revascularization procedure is available. Fixation and protection of the interposition graft are important for stable anastomosis, and to avoid mechanical injury after operation. Here, we describe a new technique for fixation and protection of the interposition graft in bonnet bypass. The interposition graft is passed through a bone groove created in the skull, and covered with microplates, temporal fascia, and muscle. The method prevents the interposition graft from slipping out during the anastomosis, and can also protect the graft from mechanical injury after the operation.