The invention relates to the technical field of steelmaking, and provides a special continuous casting crystallizer protection slag for bloom type easy-cutting steel. The protection slag comprises thefollowing components of, by weight, 27%-32% of CaO, 40%-43% of SiO2, 1%-4% of MgO, 3.5%-6% of Al2O3, 1%-4% of Na2O, 0.77%-4% of F-, 0.19%-1% of Li2O, 0.25%-1.47% of B2O3 and 8%-14% of C. The protection slag can solve the problems that the molten steel surface is prone to generate large slag strips, and the surface of a casting blank is not smooth in the continuous casting process of the easy-cutting steel. The invention further provides a method for preparing the protection slag by taking wollastonite, carbon-free soot, glass powder, fluorite, clinker, white alkali, carbon black, amorphous graphite, clay, lithium carbonate, borax, calcite, magnesia and bauxite as raw materials. The invention further provides a bloom type easy-cutting steel continuous casting method using the protection slag in the continuous casting process. The casting blank prepared by using the method is good in quality.