Abstract: The effect of Mn/S(mass ratio) on sulfide inclusions in non-quenched and tempered steel containing sulfur was studied by smelting with vacuum reduction furnace and forging in laboratory. It is found that the distributions of sulfides both in ingots and bars tend to be more dispersed with the increase of Mn/S; and it is beneficial to make the sulfides be globular or spindle with the increase of Mn/S because the percentage of sulfides whose length-width ratio is less than 3 is increased from about 5% to more than 25%. The recommended Mn/S ratio is about 40 under the experimental conditions.