The phenomena of floating, sinking, wall hanging and sticking in the mixing process of rubber powder and asphalt in a stirred tank were studied, the mixing tank model of rubber asphalt was established, and the mixing process inside the tank with solid-liquid two-phase numerically simulated in a unsteady state based on CFD software. The effects of the blade diameter, blade position, baffle and stirring speed on the mixing uniformity were analyzed. The results showed that the suitable size and position of blade were beneficial to the form of cyclic axial flow and reduction of steady flow. The installation of the baffle reduced the occurrence of tangential flow. The stirring speed did not affect the basic form of internal flow, but the suitable speed improved the mixing uniformity. In addition, the mixing uniformity matched up with the simulation results, and under the agitator parameters of blade diameter 800 mm, blade position 680 mm, blade width 100 mm, and rotational speed 280 r/min, the distribution of rubber particles after optimization was more uniform at the mixing uniformity of 0.24, which was in the complete off-bottom suspension, fitting well to the simulation results.