Abstract: The fluid-thermal-solid coupling numerical simulation of the KR impeller was conducted using Ansys software. The equivalent stress and total deformation of the impeller were calculated under centrifugal force, CFD pressure load and temperature load. The positions of maximum stress and maximum total deformation on the impeller were identified, and the influence of molten-iron temperature and eccentric stirring process on the equivalent stress and total deformation of the impeller was further analyzed. The results show that the equivalent stress at the joint of the impeller is the highest at 10.01 MPa under the non-eccentric condition. At the same time, the most significant deformation occurs at the lower part of the impeller end face, which is 15.64 mm. When the molten iron temperature is taken into account, the equivalent stress at the upper portion of the impeller joint increases from 0.77 MPa to 10.01 MPa, which twelve-fold rise, and the maximum total deformation at the lower part of the impeller increases by nearly thirteen times, thereby indicating that the molten iron temperature is the dominant factor affecting both the equivalent stress and overall deformation of the impeller, and thus must not be overlooked in analysis. The eccentric stirring of the impeller increases the overall flow velocity of the molten iron, which promotes mixing between the desulfurizer and the molten iron. At an eccentricity of 100 mm, the mixing time is reduced by 3%, but excessive eccentricity can cause splashing and oxidation of the molten iron. When the eccentricity reaches 200 mm, the equivalent stress at the upper part of the impeller joint increases by 111 times, and the total deformation at the lower part of the impeller increases by 60.33%. Excessive stress can lead to internal fractures of the impeller and external cracks, ultimately resulting in impeller failure. Similarly, excessive deformation of the impeller will reduce the impeller’s tensile strength, degrade its performance, and cause fatigue failure.