Magnesia zirconia brick containing 11 wt％ zirconia was prepared with magnesia and manoelinic zirconia as starting materials in order to replace the chrome-containing materials for RH furnace.The corrosion resistance of magnesia zirconia brick and fused rebonded magnesia chrome brick ( short for magnesia chrome brick) to high and low basicity slag of RH furnace was comparatively researched by rotary slag method and their slag resistance mechanisms were analyzed.The results show that:( 1 )because the reaction layer containing CaZrO3 forms in magnesia zirconia brick,it has better corrosion resistance to high basicity slag than magnesia chrome brick,however,it has worse corrosion resistance to low basicity slag than magnesia chrome brick; (2) ZrO2 in the magnesia zirconia brick can absorb CaO in the slag,which decreases the basicity of slag and increases the viscosity of slag,so the degree of slag penetration in magnesia zirconia brick decreases ; (3) there is little zirconia in the slag layer of residual magnesia zirconia brick; from working face to original brick layer,the residual magnesia zirconia brick shows three layers:obviously deteriorative layer,slightly deteriorative layer,and original brick layer,but the residual magnesia chrome brick only shows two layers:obviously deteriorative layer and original brick layer;the SiO2 content of residual magnesia zirconia brick is the highest in the slightly deteriorative layer,however,the SiO2 content of residual magnesia chrome brick gradually decreases from working face to original brick layer.