The invention discloses a preparation method of strong-acidity polystyrene cationic exchange resin, comprising the steps of mixing well methyl styrene, methylene bisacrylamide, and methylbenzene, adding pre-processed rice hull and gelatin solution, mixing well, adding tert-butyl peroxy-2-ethylhexanoate, heating and stirring, heating, holding the temperature, aging, and filtering to obtain polystyrene microspheres; feeding the polystyrene microspheres into n-heptane for swelling, dropwise adding sulfuric acid solution while stirring, adjusting the temperature after dropwise adding, stirring, washing with ice water, and filtering to obtain the strong-acidity polystyrene cationic exchange resin. The pre-processed rice hull is prepared by: stirring rice hull and kaolin, feeding into an anaerobic muffle furnace, heating for calcining, cooling, grinding, adding nitric acid solution, stirring, washing until neutrality, drying, adding hyperbranched polysiloxane and acetone, ultrasonically treating, treating with microwave, and drying by spraying.