We report the development of a new high oxygen pressure synthesis method of orthorhombic and twin-free RE2Ba4Cu7Oy (RE247, RE = rare earth elements) superconductors and their tri-axial orientation using by a modulated rotation magnetic field. By the new synthesis method using quartz ampoule and a chemical reaction generating additional source of oxygen pressure in it, we have successfully fabricated RE247 (RE=Y, Er) polycrystals in the almost same synthesis conditions with those using a high oxygen pressure furnace. Furthermore, tri-axial orientation of these RE247 powders has been successfully accomplished using a modulated rotation magnetic field. Although our experimental studies on the magnetic orientation were performed in epoxy resin, high degrees of in-plane orientation less than 6° were achieved. Especially for RE=Y, the degree of in-plane orientation was found to be less than 1.5°, and high effectiveness of this tri-axial orientation technique was shown in principle.