The invention belongs to the technical field of polystyrene materials and discloses a high-rigidity high-fluidity polystyrene composition and a preparation method and application thereof. The polystyrene composition comprises the following components in percentage by mass: 65-80 percent of high impact polystyrene, 15-25 percent of transparent polystyrene, 5-10 percent of a mineral filler and 0-8 percent of aids, wherein the fusion index (200 DEG C, 5Kg) of the high impact polystyrene is 3-6g/min; and the particle size of rubber is 0.5-3 microns. In the composition, the high impact polystyrene of special rubber particle size and a flexibilizer of proper molecular weight and rubber size and distribution are preferentially selected, the composition has high rigidity and high fluidity, and a loudspeaker box of a complex structure can be directly formed. Moreover, due to the addition of the mineral filler, the material density is improved, the dimensional stability and sound insulation effect of the product are improved, the mechanical property is maintained, the composition can be widely applied to the field of audio-visual equipment and is particularly applied to the manufacture of loudspeaker boxes, and an excellent low-pitch tone quality can be obtained.