The invention provides a method for preparing polystyrene-polyvinyl alcohol (PS-PVA) double-layer hollow microspheres. In the method, the yield of PVA-coated PS microspheres is increased by changing the concentration of a PVA solution and the mixture ratio of an oil-phase organic solution; the thickness of the PVA layer is controlled by adjusting the concentration of the PVA solution and the relative magnitude of a three-phase flow speed; a rotary curing mode is adopted, and hydrophobic pretreatment and adjustment of the rotation speed and the curing temperature are performed on a rotary evaporation bottle, so that hydrophilic bonding of PS-PVA composite emulsified particles in a curing process with the rotary evaporation bottle is improved. Meanwhile, direct collision and combination of the PS-PVA composite emulsified particles is avoided, the quality of a PVA coating is effectively enhanced, and the PS-PVA double-layer hollow microspheres of which the inner diameters are 800-1,300 [mu]m and the polyvinyl alcohol layer thickness deviation is 1 [mu]m are prepared successfully. By adopting the method, the channel diameter of a generator can be changed according to the demand for a target microsphere diameter. The method is easy to operate, and can be applied widely.