The invention discloses an automatic material cut-off device for a one-mold multi-output two-plate injection mold. The automatic material cut-off device comprises a runner sliding block 1, a core plate 2 and an oblique guide column 3. The adopted runner sliding block is provided with a main runner, auxiliary runners, a main sprue, auxiliary sprues, an oblique guide hole and T-shaped sliding rails. The core plate is provided with T-shaped sliding grooves and cores. The core plate is located on a movable mold. The runner sliding block is buckled into the T-shaped sliding grooves of the core plate through the T-shaped sliding rails in a sliding manner. The auxiliary sprues communicate with the cores in a contacting manner. The oblique guide column is fixed to a fixed mold. In the mold closing state, the oblique guide column is inserted into the oblique guide hole of the runner sliding block in a sliding manner. In the working process, the oblique guide column pushes the runner sliding block to slide leftwards to cut off and separate products and cold slug at the auxiliary sprues, then product ejector rods eject the products to be separated from the cores, meanwhile, slug ejector rods eject the cold slug to be separated from the runner sliding block, and according to the technical scheme, manufacturing of the automatic material cut-off mechanism of the one-mold multi-output injection mold achieves the purposes of improving efficiency and reducing cost.