The invention discloses a styrene-acrylate aqueous dispersoid with an amphiphilic structure and a preparation method thereof. The preparation method comprises the following steps of: mixing 1-10 parts of reactive emulsifying agent, 14-38 parts of styrene, 12-32 parts of alpha-methyl styrene, 40-60 parts of acrylate monomer, 1-2 parts of initiator and 0-1 part of chain transfer agent, and preparing into a composition A; dissolving 0.2-0.5 part of initiator in 2-5 parts of solvent, and preparing into a composition B; adding 30-50 parts of solvent into a reaction kettle, rising the temperature to 80-100 DEG C, firstly adding 10-20 parts of composition A, reacting for 20-40 minutes, then dropping the remaining amount of the composition A, and then adding the composition B; and adding 13.5-20.2 parts of amine substances into the reaction kettle for carrying out neutralization, dispersing reaction products with water and obtaining the styrene-acrylate aqueous dispersoid. The styrene-acrylate aqueous dispersoid prepared by the invention has the characteristics of high solid content, low viscosity, fast drying, excellent storage stability and the like, the process is simple, and the safety and the energy conservation are achieved.