The invention discloses an ice breaking cutter for an icebreaker, and relates to the technical field of icebreakers. An outer hull plate installed at the bottom of the icebreaker comprises a bottom plate and two symmetrically arranged side plates, wherein the side plates, the bottom plate and the outer hull plate form a totally enclosed structure through full penetration welding; a continuous structure penetrating through the whole ship of the icebreaker is adopted, a sharp bow is arranged on the bow part, a stern adopts a structure transiting from gradual width to straight, and a frame plateis arranged at each rib position; and a plug welding panel for welding and fixing the side plates is arranged on one sides of the frame plates. According to the ice breaking cutter, finite element analysis is carried out, appropriate materials and excellent welding materials and welding processes are selected, so that the overall structural strength of the ice breaking cutter is improved, the icebreaking thickness is increased, the ice breaking efficiency is improved, a more economical channel is developed, and the rescue speed for trapped ships is improved.