Fused magnesia calcium sand (granularity 5~3, 3~1 and ≤1 mm) is used as aggregate, fused magnesia (≤0.074 mm) as the matrix, and 3% (w) of large scale graphite (≤ 0.149 mm), fine flake graphite (≤0.044 mm), and microporous graphite (≤0.074 mm). Three kinds of ultra-low carbon MgO-CaO-C brick samples were prepared, and their high-temperature strength, oxidation resistance, and resistance were compared. Thermal shock and slag erosion resistance. The results show that: (1) The type of graphite has little effect on the physical properties of ultra-low carbon MgO-CaO-C bricks. (2) Ultra-low carbon MgO-CaO-C bricks made of large flake graphite have better oxidation resistance and slag erosion resistance, while samples made of microporous graphite have the best thermal shock resistance; considering the overall performance, The carbon source is best added in the composite form of 1.5% (w) large flake graphite and 1.5% (w) microporous graphite.