The invention discloses a double-end-face numerical control chamfering machine tool and method for an ultra-large internal tooth gear. The machine tool comprises a numerical control rotary table, a horizontal radial sliding table, a first stand column, a second stand column, a Y1 tool rest assembly, a Y2 tool assembly, a Y3 tool rest assembly, a Y4 tool assembly, an X1-axis radial feeding system,an X2-axis radial feeding system, a Y1-axis vertical feeding system, a Y2-axis vertical feeding system, a Y3-axis vertical feeding system, a Y4-axis vertical feeding system, a steel brush deburring system and workpiece supports. According to the double-end-face numerical control chamfering machine tool, the motion mode that a workpiece is fixed and the machine tool does rotary motion is adopted, the occupied area of the numerical control machine tool for chamfering an ultra-large gear is greatly reduced, simultaneous chamfering of the end faces of the two sides of the ultra-large internal tooth gear is achieved through a hard alloy milling tool rotating at a high speed, chamfers are adjustable in size and shape, the sizes of the chamfers are consistent, tooth grooves are automatically centered, and deburring and polishing work can be carried out on tooth roots, tooth tops and other parts. The machine tool is innovative in structure, low in manufacturing cost and high in automation degree.