The invention discloses novel stemming at a tap hole. The stemming comprises the components in parts by weight as follows: 5-25 parts of corundum, 5-25 parts of high aluminum aggregate, 10-30 parts of silicon nitride combined with silicon carbide, 2-3 parts of silicon nitride iron, 5-15 parts of coke powder, 8-20 parts of clay, 1-5 parts of crystalline flake graphite, 5-10 parts of pyrophyllite, 4-7 parts of sericite, 5-10 parts of magnesium-aluminum spinelle, 2-4 parts of active alumina micro powder, 1-3 parts of metal powder and 15-20 parts of external composite binding agent. The composite binding agent comprises tar, modified phenolic resin and an organic solvent. The volume ratio of tar, modified phenolic resin to the organic solvent in the composite binding agent is 1:3:1. According to the invention, with the adoption of the composite binding agent formed by mixing tar and modified phenolic resin, smoke generated is less, the same plasticity to be combined with tar is met, the opening performance is good, the pressure resisting thermal shock resistance is good, and the adhesion strength is high. The depth of the tap hole can be prolonged and the furnace cylinder can be protected, the tapping time is prolonged, and the number of casts every day is reduced.