The invention provides a multifunctional machining device for precise metal structural parts, which comprises a supporting table, a supporting column, a movable brake wheel, a threaded hole, a machining table, a slidable supporting anti-shaking block structure, a rotatable measurement positioning frame structure, a slidable protective grinding seat structure, an adjustable rotating dust hood structure, a locking nut, a sliding seat, a cutting groove and a first pull rod, the polishing device comprises a supporting table, a polishing motor, a precise polishing wheel, a threaded column, a bottom plate, a first rotating rod, a fixing cover, a dust collector mechanism, a first sliding groove and a sliding hole, and supporting columns are connected to the four corners of the lower end of the supporting table through bolts correspondingly. Through the arrangement of the jacking block, the sliding plate, the sliding rod, the supporting rod, the supporting plate, the machining table, the locking nut, the first sliding groove and the sliding hole, the jacking block can be supported through cooperation of the supporting rod and the supporting plate in the using process, and errors caused by shaking of the jacking block in the cutting process are prevented.