The invention discloses a casting method of a spheroidal graphite cast iron valve, and relates to the spheroidal graphite cast iron valve. The method comprises the steps of model making, modeling, smelting, pouring, heat treatment and obtaining of a finished product valve casting. Alloy elements are not added, the spheroidal graphite cast iron valve with the supersize can be stably produced, a dedicated slag blocking device is arranged at the front end of a transverse sprue, when molten iron of the transverse sprue is introduced into the front end, the slag blocking effect is achieved, it is ensured that a mold cavity is rapidly and stably filled with the molten iron, oxide inclusions are reduced, a heat preservation top riser is adopted, and is placed on the top of the valve, and castingfeeding, slag discharging and exhausting are facilitated; a chilling block is arranged at the position, on the large and thick section and the portion with the large wall thickness difference, in thecasting, chromite sand is used around an even core and a shaft head in a shaft hole of the casting, the upper portion of an annular belt is paved with chromite sand, it is ensured that the casting canbe subject to directional sequential solidification, and meanwhile, the casting surface quality is ensured, and the method is particularly suitable for making a spheroidal graphite cast iron water and electricity butterfly valve with the supersize and the large section.