The invention provides a steel-making desulfurizing agent, a desulfurizing method thereof and a steel making method. The steel-making desulfurizing agent mainly comprises the following raw materials including 1-2 kg/t Fe fluorite, 8-9 kg/t Fe lime, 0.25-3.3 kg/t Fe aluminum particles and/or AD powder according to the weight ratios of the raw materials to molten iron. According to the steel making method, the technology route that vanadium is extracted firstly, and then sulphur is removed is adopted. Deoxygenation can be carried out on semisteel while the desulfurizing agent carries out desulfurizing; and the refined desulfurizing pressure is greatly reduced, and the content of sulphur in finished steel is reduced to be lower than 0.002%. The desulfurizing agent is simple in component and convenient to use. The steel making method thoroughly eliminates the problem of contamination of vanadium slags.