The invention relates to the field of spheroidal graphite cast iron, in particular to high-strength low-temperature-resisting spheroidal graphite cast iron and a preparing method thereof. The spheroidal graphite cast iron comprises, by mass percent, 3.2% to 3.5% of carbon, 2.1% to 2.3% of silicon, 0.4% to 0.5% of manganese, 0.4% to 0.6% of copper, 0.2% to 0.4% of nickel, 0.2% to 0.4% of molybdenum, 0.04% to 0.06% of magnesium, 0.05% to 0.08% of chromium, 0.005% to 0.008% of titanium, 0.002% to 0.003% of vanadium, not larger than 0.04% of phosphorus, not larger than 0.02% of sulphur and the balance iron. The preparing method of the high-strength low-temperature-resisting spheroidal graphite cast iron comprises following steps: firstly, raw materials are smelted; secondly, spheroidizing treatment and inoculation are carried out; and thirdly, heat treatment is carried out. Through reasonable arrangement of all element components, the tensile strength of the spheroidal graphite cast iron is improved, a proper nucleating agent is prepared, internal inoculation matched with inoculation in a ladle is adopted, the inoculation effect is reinforced, meanwhile, during heat treatment, the heating temperature, the heat preservation time, the cooling rate and the manner are reasonably arranged, the strength and low temperature resistance of the iron are effectively improved, the spheroidal graphite cast iron is high in strength and excellent in low temperature resistance, and the preparing method is simple and efficient.