The invention discloses a preparation process for a refractory brick on a ladle slag line. The preparation process comprises the following steps of (1) placing waste magnesia bricks, fused magnesia, silicon carbide, zirconia, fused millite and magnesite powder into a mixer to be mixed for about 45-60 minutes; (2) adding graphite powder, asbestos fibers, Suzhou bentonite, zirconium boride, boron nitride and cerium oxide, and mixing for about 120-135 minutes; (3) adding asphalt powder, phenol formaldehyde resin, sodium hexametaphosphate and water, and further mixing for about 150-180 minutes; (4) molding by using a press machine, and drying a green brick at the temperature of 200 DEG C for 24 hours; and (5) calcining at the temperature of about 1800-1840 DEG C, and preserving the heat for about 16-18 hours. The refractory brick prepared by using the preparation method has the following excellent performances: molten steel is recarburized by at most 2.3ppm, the volume density is 3.05-3.15g/cm<3>, the apparent porosity is 1.5-2.5%, the normal-temperature compressive strength is larger than or equal to 45MPa, the 1400-DEG C high-temperature bending strength of buried carbon is larger than or equal to 33Mpa, and the 1400-DEG C linear expansion coefficient is 1.35-1.45%. Through measuring the thermal shock resistance of the refractory brick prepared by using the preparation process disclosed by the invention by using an air quenching method comprising the step of carrying out air cooling once at the temperature 1100 DEG C, the residual strength retention rate is measured to be 74-76%.