The present invention discloses a composition for a desulfurizer with a high sulfur capacity and a process for making the same. The composition comprises the active components of three kinds of iron oxides and is used in the desulfurizer to remove hydrogen sulfide from the gaseous and liquid state feed stocks. The above-mentioned composition comprises cubic ferroferric oxide in the form of crystalline phase (Fe3O4), amorphous ferric oxide (Fe2O3) and amorphous ferric oxide monohydrate (Fe2O3.H2O). The composition has a sulfur capacity of at least 40%. The process for preparing the composition comprises the following steps: (1) mixing a solid ferrous compound with a solid hydroxide at a molar ratio of iron to hydroxyl being in the range from 1:2 to 1:3; (2) kneading the mixture feeds obtained in step (1) and making them react completely; (3) drying the products obtained in step (2) in the air; (4) washing and filtering the feeds obtained in the step (3); (5) naturally drying or baking the solids obtained in step (4) to form a composition for a desulfurizer with a high sulfur capacity. The process of the present invention is simple and easy to operate, consumes less energy and produces the products with a stable quality.