The invention discloses a nylon/polystyrene alloy microsphere, a preparation method and applications thereof, wherein the nylon/polystyrene alloy microsphere comprises, by weight, 25-95 wt% of pore-containing nylon microsphere, and 5-75 wt% of polystyrene uniformly dispersed in the pores and/or on the surface of the pore-containing nylon microsphere in a nanometer or micro particle manner or/and in a micro-scale continuous state manner, wherein the alloy microsphere is spherical or nearly spherical particle with a particle size of 0.05-500 [mu]m. According to the present invention, the nylon/polystyrene alloy microsphere can be used in the fields of chromatographic separation, drug delivery and sustained-release, functional coating materials and 3D printing selective laser sintering.