The invention discloses an unfired magnesia-calcium brick which is prepared from the following raw materials in percentage by weight: 9-16 percent of 5-7mm magnesia-calcium sand, 9-16 percent of 3-5mm magnesia-calcium sand, 9-16 percent of 1-3mm magnesia-calcium sand, 9-16 percent of 0.5-1mm magnesia-calcium sand, 4-16 percent of 0.5-1 mm magnesia sand, 5-25 percent of not larger than 0.5mm magnesia sand, 1-10 percent of graphite, 2-5 percent of anhydrous resin bonding agent and 1-3 percent of additive formed by mixing magnesia powder and zircon sand. The processing method comprises the following steps of: crushing, grinding, compounding, pressing and forming, heating, baking and carrying out waterproof treatment. In the invention, the unfired magnesia-calcium brick with great volume density and high compression strength can be prepared due to reasonable compounding and a scientific treatment process, and particularly, the additive formed by mixing the magnesia powder and the zircon sand is used, therefore, the product has good medium-temperature strength, waterproofness and crack resistance.