The invention relates to a production method of a low-carbon sulfur series free-cutting steel continuous casting billet. The method comprises the steps of: first placing scrap steel into a converter, then loading liquid iron into the converter; conducting top-bottom combined blowing; carrying out tapping; performing deoxygenation and alloying; implementing argon blowing treatment; conducting soft argon blowing after alloy fine adjustment; adding carbonized rice hulls into a steel ladle when the argon blowing is over; starting continuous casting when the molten steel temperature reaches 1530-1570DEG C; and employing a continuous casting process of tundish treatment, crystallizer control, secondary cooling, straightening and cutting. The invention has the characteristics that: the smelting is free of desulfurization, LF refining treatment and other processes, no steel breakout phenomenon exists in casting, the composition control is stable, the yields of S and Mn elements are both above 90%, the cutting-tool wear can be reduced during processing so as to improve the service life, the tundish has a high utilization rate, the continuous casting billet has no subcutaneous bubble, heart crack, surface crack and other defects, and is free of composition segregation, and the inclusions in the casting billet are thick, big and in a spherical shape, thus being in favor of shape control of the rolled inclusions and improvement of the steel cutting performance.