The invention discloses an aluminum alloy plastic suction die. The aluminum alloy plastic suction die is composed of the following raw materials including, by weight percent, 0.8%-1.2% of copper, 0.06%-0.08% of ferric oxide, 1%-1.8% of magnesium, 3%-4.5% of zinc, 0.01%-0.04% of chromium, 0.3%-0.5% of silicon dioxide, 0.02%-0.05% of rare earth elements, 0.05%-0.2% of manganese and the balance aluminum and inevitable impurities. A preparing method of the aluminum alloy plastic suction die includes the specific steps that firstly, materials are prepared; secondly, a model is designed; thirdly, pretreatment is conducted; fourthly, smelting is conducted; fifthly, casting is conducted; sixthly, heat treatment is conducted; seventhly, coating of a protection layer is conducted; and eighthly, polishing is conducted. Aging treatment and second-stage type heating treatment are conducted on a cast product, and the service life of the product can be prolonged. The surface of the product is coated with a wear-resisting layer, so that wear resistance of the die is improved; and the surface of the die is polished and cleaned, and smoothness of the surface of the product is good.