The invention discloses a molding machining die assembly. The molding machining die assembly is characterized in that a forming step groove and a plurality of sliding grooves distributed around the forming step groove are formed in the bottom of a die groove of a lower die, sliding blocks capable of being slidably installed are arranged on the sliding grooves, supporting springs are arranged on the sides, away from the forming step groove, of the sliding blocks, supporting surfaces and first guide surfaces obliquely arranged are arranged on the sides, close to the forming step groove, of the sliding blocks, a profiled bulge matched with a die groove is arranged at the bottom of an upper die, a second guide surface matched with the first guide surface is arranged on the periphery of the profiled bulge, and the lower end of a positioning column penetrates through a second positioning hole of the upper die to be in threaded fit with a first positioning hole of the lower die. According tothe molding machining die assembly with the optimized design, the structural design is reasonable, the upper die is pressed down through a boss, the positioning column is roughly positioned through amiddle opening of a metal plate, the sliding blocks are enabled to move towards the outer periphery through the first guide surfaces and the second guide surface, so that the metal plate slides downwards along the first guide surfaces and accurately falls on the forming position, and then the forming position is ensured to be accurate.