The invention discloses low alloy cast steel. The low alloy cast steel is produced from the following components in percentage by weight relative to the total weight of the low alloy cast steel: 0.20%-0.30% of carbon, 0.20%-0.40% of silicon, 0.95%-1.05% of manganese, phosphorus which is smaller than or equal to 0.020%, sulfur which is smaller than or equal to 0.020%, 0.45%-0.55% of chromium, 0.50%-0.60% of nickel, 0.35%-0.45% of molybdenum, 0.02%-0.06% of aluminum, 0.01%-0.05% of niobium, copper which is smaller than or equal to 0.20%, aluminum and niobium which are greater than or equal to 0.03% and smaller than or equal to 0.09%, and the balance being ferrum and other unavoidable elements. The performance of the low alloy cast steel after normalizing treatment and modified treatment is that the tensile strength is greater than or equal to 931MPa, the yield strength is greater than or equal to 793MPa, the extensibility is greater than or equal to 14%, the area reduction rate is greater than or equal to 30%, the charpy V type impact power at minus 40 DEG C is greater than or equal to 35J, and the hardness range is 288HBW-325HBW. The low alloy cast steel has superior solderability, can be usually used for preparing railroad locomotive vehicle parts, such as coupler bodies, coupler knuckles, coupler yokes and the like, can also be used for other parts and components having the equal mechanical property requirements.