Low alloyed bainite ductile iron can be obtained with the heat treatment technics of oil quench-ing and isothermal tempering. The effects of the austenitizing temperature and the isothermal temperature on the properties of ductile iron are researched. Results show that the matrix microstructure is needle like bainite after the treatment of oil quenching and isothermal tempering and the material mechanical properties of ductile iron get great improvement. The hardness reaches to 56.7 HRC, the impact toughness reaches to 74.5 J•cm-2, while the tensile strength reaches to 1372.9 MPa. the hardness and tensile strength increases begin and then declines with the rise of the austenitizing temperature. Impact toughness declines gradually with the rise of the austenitizing temperature, and increases with the rise of the isothermal temperature. The better processing parameters in this paper as follows. The austenitizing temperature is 920 ℃, while the isothermal temperature is 300 ℃.