The invention discloses A356.2 casting aluminum alloy and a method for adding titanium into a pre-furnace for the A356.2 casting aluminum alloy. The method comprises the steps of 1, preheating a titanium agent; 2, heating A356.2 electrolytic raw molten aluminum to the temperature not lower than 840 DEG C; 3, pumping the A356.2 electrolytic raw molten aluminum obtained in step 2 into the pre-furnace through a siphon, and meanwhile, supplying the titanium agent obtained after preheating of step 1 into the pre-furnace so that titanium-added molten aluminum can be obtained; and 4, smelting the titanium-added molten aluminum so that the A356.2 casting aluminum alloy can be obtained. Compared with the traditional A356.2 casting aluminum alloy smelting operation titanium agent adding process, bymeans of the method, the temperature raising process implemented before the titanium agent is added is omitted; the phenomenon that the titanium agent is not molten completely, so that the titanium agent sinks to the bottom is reduced; fluctuation of the titanium element is reduced; and the casting yield of the titanium agent is increased by 10%, and energy and time are saved.