The invention relates to a large-sized, high-strength and high-toughness 7000 series aluminum alloy round cast ingot and a preparation method thereof to solve the problems of low strength and low fracture toughness property of an existing large-sized 7000 series aluminum alloy round cast ingot. The aluminum alloy round cast ingot is manufactured by Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti, Zr, Sb, Be, Na, Li, K and the balance Al. The preparation method comprises the following steps that step 1, that raw materials are weighed; step 2, a smelt agent is laid at the bottom of a furnace before raw materialfeeding, the raw materials are added into the smelting furnace, and then the smelt agent is laid on the surface after raw material feeding; step 3, heating is conducted until the raw materials in thefurnace smelt, and then a copper plate and zinc ingot are added; step 4, smelting is carried out, and dross on the surface is removed; step 5, refining is carried out; step 6, turning down is carriedout; step 7, casting is carried out; step 8, saw cutting is carried out, and step 9, homogenizing annealing is carried out. The aluminum cast ingot manufactured section steel has high tensile strength, compression-resisting yield strength and high fracture toughness property, and is used in the field of aluminum alloy.