The invention discloses casting powder for high-aluminum steel continuous casting and a preparation method thereof and an application. The casting powder for high-aluminum steel continuous casting adopts A203-MgO-B203 as a slag system, with Al203, MgO, B203 as a main substrate, and adopts CaO, MnO, SiO2, CaF2, Na2O, K2O, Li2O,C as raw materials meanwhile, all the materials are mixed and spray granulated to prepare the casting powder. The casting powder is low in melting point and viscosity and good in lubricating performance, when the casting powder is used for high-aluminum steel production,the degree of slag-steel reaction can be reduced, the surface quality of a casting blank can be improved, defects such as pits and cracks are reduced, and the production qualified rate of the castingblank is improved. According to the method, the consumption of CaF2 in the casting powder is reduced, the influence of continuous casting process on the environment is reduced, meanwhile, the preparation process is simple, and industrial production is easy to implement.