The invention provides a crystallizer covering slag for continuously casting high-manganese high-aluminum steel and preparation method of the crystallizer covering slag. The covering slag is prepared from the following components in parts by weight: 20-38 parts of CaO, 20-35 parts of Al2O3, 5-18 parts of SiO2, 10-22 parts of BaO, 2-7 parts of Li2O, 5-12 parts of F<->, 1-4 parts of MgO, 2-8 parts of C and Fe2O3 which is less than or equal to 2 parts. According to the preparation method disclosed by the invention, wollastonite, limestone, quartz sand, fluorite, bauxite, barium carbonate, magnesia, soda, lithium carbonate and carbonaceous materials are used as raw materials, and the covering slag is prepared through the following steps of: calculating of consumption, melting, smashing, fine grinding, drying and granulation. The covering slag disclosed by the invention has the characteristics of being low in reactivity and good in property stability, the lubrication and the thermal transmission of casting blanks can be effectively coordinated and controlled, the smooth performing of the continuous casting process of the high-manganese high-aluminum steel can be guaranteed, high-manganese high-aluminum steel continuous casting blanks with excellent surface quality are cast, and multi-heat continuous casting can be realized.