The invention discloses a preparation method of an automobile dash sound insulation pad, wherein the preparation method comprises the steps: S1, material cutting: firstly selecting a cotton felt, a PU foam board and a sound insulation cotton board with proper sizes, then preparing a mold plate of an automobile dash board, putting the cotton felt, the PU foam board and the sound insulation cotton board on the mold plate, and cutting according to the shape of the mold plate. The invention relates to the technical field of sound insulation of automobile dash boards. In conclusion, according to the preparation method of the automobile dash sound insulation pad, through the working procedures from S1 to S4, the cotton felt and the sound insulation cotton plate are bonded through an adhesive, silicon-coated protective paper and a adhesive sticker, so that the cotton felt can be easily taken down, the disassembly difficulty is greatly reduced, the disassembly efficiency is improved, and the replacement cost is low due to the fact that the cost of the cotton felt is low; and finally, a side edge of a final cut edge is wrapped with an adhesive tape, the cut edge is prevented from being polluted, the side edge is wrapped and limited, and the situation that the use quality of the whole connection is affected due to damage of the side edge is avoided.