The invention provides a universal grinding carriage for internal gears and external gears of a formed grinding wheel gear grinding machine, comprising a horizontal cantilever; the lower end surface of the horizontal cantilever is connected and fixed with a vertical grinding arm by a bolt; and the side surface of the lower end of the vertical grinding arm is fixed with a grinding head component. The grinding carriage is directly arranged on the formed grinding wheel gear grinding machine and not only can process external gears, but also can process internal gears; when the external gears are ground, the whole grinding carriage is rotated by 180 degrees only, and the grinding carriage has good rigidity; when helical gears are ground, a grinding wheel can not generate interference with workpieces; the grinding wheel has convenient repair and maintenance, low cost and high cost performance.