Influence of pressure applied on the mold after pouring on the surface status and mechanical properties of aluminum castings in lost foam casting is investigated. The results showed the applied pressure is beneficial to eliminate grainy surface and cold shut because of improving filling ability. It improves the tensile strength and density slightly as a result of depression of pore formation. Prolonged time difference between pressures applied on both gate and casting surface results in the casting surface boss and burning on. Inadequate pressure maintaining time degrades the mechanical properties.