Abstract: Medium carbon steel for oil casing was manufactured by changing tundish superheat (20, 40 ℃), mass ratio of Ca to S in the molten steel (0-0.9), roughing single pass deformation (14%, 20%), intermediate billet thickness (49, 52, 53 mm), and last three-pass cumulative deformation of finishing rolling (29%, 34%). The effect of tundish superheat, rolling deformation and mass ratio of Ca to S on the microstructure and impact energy at -10 ℃ of the test steel was analyzed. The results show that at tundish superheat of 20 ℃, the center segregation and carbon segregation of continuous cast billets were reduced, and the distribution of the segregation changed from lines and chains to points. The higher the rolling deformation, the smaller the grains, the lower the banded structure degree, and the larger the low temperature impact energy of the test steel. With the increase of mass ratio of Ca to S, the low temperature impact energy of the test steel increased. The optimal production process parameters were listed as follows: tundish superheat at 20 ℃, mass ratio of Ca to S no less than 0.4, roughing single pass deformation of 20%, intermediate billet thickness of 53 mm, and last three-pass cumulative deformation of finishing rolling of 34%. No band structure existed in the steel plate manufactured with the optimal process, and the low temperature impact energy was much higher than the standard requirement.