The invention discloses a low-temperature steel bar and a production method thereof, the chemical composition of which is calculated by mass percentage: Ni 0.8-0.9%, Mn 1.6-1.7%, Si 0.3-0.4%, C 0.04-0.08%, Al 0.01-0.02 %, P≤0.007%, S≤0.004%, O≤0.002%, N≤0.003%, As≤0.005%, H≤0.0002%, and the rest are Fe and unavoidable impurities. The production methods include KR molten iron pretreatment, Converter smelting, LF furnace refining, RH furnace refining, continuous casting and rolling. The invention completes the composition design and mass production of the low-temperature steel bar at a relatively low cost, and achieves the effects of strictly controlling impurity elements, inclusions and surface quality, and reducing low-temperature brittleness.