In the investigation, the structure and working principle of a vane compounder dominated by dynamic tensile deformation were introduced, and PS/HDPE melt blending experiments were conducted on the vane compounder and a commercial Brabender rotor internal mixer dominated by shear deformation. Then, the influences of the rotating speed and the mixing time on the mechanical property, rheological property and microstructure of the blends were discussed. The results show that (1) the tensile strength of the PS/HDPE blends molded by the vane compounder first increases and then keeps stable with the increases of the mixing time and the rotating speed, which is similar to those of the Brabender rotor internal mixer; (2) as compared with the Brabender rotor internal mixer, the rotating speed of the vane compounder has a smaller effect on the particle size of the dispersion phase of the blends, and the vane compounder needs a shorter time to achieve the same particle size of the dispersion phase at the same rotating speed; (3) the apparent viscosity of the blends molded by the Brabender rotor internal mixer remains unchanged with the increases of the mixing time and the rotating speed while that of the vane compounder decreases; and (4) the vane compounder shows a higher mixing efficiency and a better mixing effect in comparison with those of the Brabender rotor internal mixer.