The mechanical properties of ductile iron samples containing 0.25% molybdenum and 0.2%~0.8% nickel were tested after being annealed at a low graphitization temperature. The microstructure and impact fracture were observed and analyzed. The ferrite content of ductile iron was increased after adding a small amount of molybdenum and nickel. Consequently, the impact toughness was increased by more than 50% while the strength and the hardness were decreased. The pearlite in the ductile iron was gradually transformed into ferrite after low temperature annealing. The impact toughness was increased substantially and the impact absorbed energy was increased to 500% compared with cast ductile iron samples. Many tearing ridges and dimples were found on the impact fracture through SEM observation. The mechanical properties in different annealing parameters were relatively more stable with a smaller fluctuation after molybdenum and nickel were added.