The invention discloses PET (polyethylene glycol terephthalate) fiber/mineral cotton fiber composite sound absorbing cotton, which is prepared from the following ingredients in pars by weight: 70 to 80 parts of PET fibers, 40 to 50 parts of mineral cotton fibers, 10 to 15 parts of emulsifying agents OP-7, 5 to 10 parts of peregal O-20, 80 to 100 parts of PP (propene polymer), 30 to 40 parts of EPDM (ethylene propylene diene monomer), 15 to 20 parts of calcined clay, 10 to 15 parts of modified kieselguhr, 2 to 3 parts of stearic acid, 5 to 8 parts of triethyl citrate, 4 to 6 parts of pentabromophenyl ethane, 2 to 3 parts of glycerin monostearate, 1 to 2 parts of isopropyl distearyl oxyaluminate, 2 to 3 parts of zinc stearate, 1 to 2 parts of calcium stearate, 0.5 to 1.5 parts of anti-aging agents TPPD and 1 to 2 parts of antioxidants 1035. 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.