The invention discloses PET (polyethylene glycol terephthalate) fiber/teflon fiber composite sound absorbing cotton, which is prepared from the following ingredients in parts by weight: 70 to 80 parts of PET fibers, 40 to 50 parts of teflon fibers, 10 to 15 parts of emulsifying agents OP-30, 5 to 10 parts of peregal O-20, 80 to 100 parts of PP (propene polymer), 30 to 40 parts of HIPS (high impact polystyrene), 15 to 20 parts of activated clay, 10 to 15 parts of modified kieselguhr, 2 to 3 parts of stearic acid, 5 to 8 parts of dioctyl adipate, 4 to 6 parts of cresyl diphenyl phosphate, 2 to 3 parts of liquid paraffin, 1 to 2 parts of 3-aminopropyltrimethoxysilane, 2 to 3 parts of calcium stearate, 1 to 2 parts of barium stearate, 0.5 to 1.5 parts of anti-aging agents RD and 1 to 2 parts of antioxidants DLTP (dilauryl thiodipropionate). The sound absorbing cotton prepared by the invention has the advantages that the appearance evenness is good, the thickness is uniform, the hand feeling is soft, the product bonding degree is good, the tensile performance is high, the sound absorbing performance is excellent, the flame retardant effect is good, and the like.