The invention discloses a QT600-3 nodular iron casting and a manufacturing method thereof. The hardness range of the nodular iron casting is between 180 and 220 HB, and the tensile strength of the nodular iron casting is more than or equal to 600 MPa. The nodular iron casting comprises 3.3 to 3.8 percent of C, 2.2 to 2.5 percent of Si, 0.2 to 0.4 percent of Mn, 0.06 to 0.08 percent of rare-earth RE, 0.03 to 0.06 percent of Mg, 0.33 to 0.4 percent of Cu, less than or equal to 0.15 percent of P, less than or equal to 0.02 percent of S, other trace impurity, and the balance being Fe. The manufacturing method thereof comprises the following steps: heating a raw material containing iron into molten iron and smelting the molten iron, and pouring the molten iron into a foundry ladle to cool; pouring the molten iron into the foundry ladle comprising nodulizing agent and copper blocks, and standing; pouring the molten iron into a mold, adding nucleating agent, and cooling the mixture; and finally obtaining the nodular iron casting through opening a box, cleaning, drawing temper, cooling, blasting ball, painting. The tensile strength of the nodular iron casting is high, and the hardness of the nodular iron casting is even.