The effect of electric fused ZrO2, m-ZrO2 and zirconite on the sintering properties of MgO-CaO bricks was studied and the effect of the ZrO2 content and temperature on BD (bulk density), AP(apparent porosity )and CCS (Cold Crushing strength) of MgO-CaO bricks was investigated. The microstructure of burned specimens was analyzed by SEM. The result shows that the sintering property is best while 5% m-ZrO2 was added at 1600℃.