Belonging to the light alloy design and preparation field, the invention relates to a moderately strong high toughness aluminum alloy material for liquid forging, in particular to a liquid forging Al-Cu-Zn aluminum alloy and a preparation method thereof. The alloy comprises the following main components by mass: 3.2-4.8% of Cu, 1.8-3.0% of Zn, 0.3-0.8% of Mn, 0.08-0.22% of Cd, 0.06-0.24% of Ti, 0.05-0.15% of V, 0.07-0.16% of Zr, 0.005-0.06% of B, 0.002-0.006% of Be, less than or equal to 0.15% of impurity element Fe, less than or equal to 0.1% of Mg, less than or equal to 0.06% of Si, less than or equal to 0.05% of other single impurity element, less than or equal to 0.3% of total impurities, and the balance Al. The Al-Cu-Zn system moderately strong high toughness aluminum alloy mentioned in the invention has the advantages of excellent formability during liquid forging forming, no hot cracking tendency, low porosity and low segregation. After heat treatment, the components prepared from the alloy have excellent strength and plasticity, superiority unmatched by other active alloys, and have broad application prospects.