To investigate the effect of multi-paddle variable-speed stirring on the uniformity of a desulfurization stirring tank, a large side-entering agitator with three evenly distributed impellers was taken as the research object. A three-dimensional transient model was established based on the Eulerian two-phase flow model and the k-ε turbulence model. The uniformity under constant-speed stirring and multi-paddle variable-speed stirring conditions was compared. The influence of solid volume fraction on variable-speed stirring was discussed, and the effects of different variable-speed patterns, amplitudes, and frequencies on the internal uniformity of the stirring tank were analyzed. The results show that variable-speed stirring can effectively reduce the accumulation area of solid particles at the bottom. Among the methods, three-impeller variable-speed stirring achieves the best effect, reducing the high solid volume fraction region volume by 13.62% compared to constant-speed stirring. As the solid volume fraction increases from 0.2 to 0.5, multi-paddle variable-speed stirring consistently reduces the non-uniformity, with better improvement at lower solid volume fractions. Larger speed amplitudes and moderate frequencies lead to better uniformity, and among various variable-speed patterns, the trapezoidal variable-speed method exhibites the best stirring performance.