The invention discloses high-manganese high-nitrogen low-nickel stainless steel plate blank continuous casting crystallizer covering slag which comprises the following components in percentage by weight: 54-57% of wollastonite, 9-13% of fluorite, 9-13% of sodium carbonate, 0-1% of lithium carbonate, 5-7% of glass dust, 8-12% of vanadine soil, 2.5-2.7% of soot carbon and 3-3.5% of graphite, and comprises the chemical components in percentage by weight: 31.9-34.9% of calcium oxide, 32.1-35.1% of silicon dioxide, 7.3-8.3% of aluminium oxide, 0.5-1.5% of magnesium oxide, 0.5-1.4% of iron sesquioxide, 4.4-6.4% of fluorion, 6.5-7.5% of sodium oxide, 0-0.39% of lithium oxide, 4.5-6.0% of fixed carbon and 4-7% of gas volatile matters. The alkalinity of the covering slag, namely the ratio of CaO to SiO2, is 0.91 to 1.00, the melting point of the covering slag is 1100 DEG C to 1160 DEG C, and the viscosity of the covering slag is 0.3 to 0.6 Pa.s at 1300 DEG C. The invention can solve the problems of easy crusting, slag entrainment, slag inclusion, slag sticking on casting blank surfaces, bubbles under skins, cracks, deep chatter mark, felting, bleed-out, and the like of the covering slag in the crystallizer during high-manganese high-nitrogen low-nickel stainless steel plate blank continuous casting, and has the advantages of uniform and stable slagging in the crystallizer, good casting blank quality, difficult felting and bleed-out, and the like.