In this study, a dynamic mixer was designed to mix polymer melts online during extrusion, and the flow of a polymer melt in a mixer was simulated using Polyflow software. The Orthogonal experiment was conducted to analyze the effects of three geometrical parameters (i.e. the length of entrance zone (Li), the gap between the rotor and wall (g), and the diameter of cone-shaped rotor (d2)) on mixing properties of a dynamic mixer. The Li, g, and d2 were optimized for the minimum product of segregation scale (S) and power consumption (P). Finally, the mixing properties of the dynamic mixer were compared with those of SK and SX static mixers. The results indicated that among the above-mentioned three parameters, the g was the most important parameter influencing S, and S∙P. The minimum S∙P of 1059 µm·W was obtained when the Li was 16 mm, the g was 1 mm, and the d2 was 24 mm. The S decreased with the increase of the rotation speed from 120 to 360 r/min, and increased with the increase of the flow rate from 15 to 45 mL/min. However, the P increased with the increase of both the rotation speed and flow rate. The maximum shear rate of the melt in the dynamic mixer was observed in the mixing zone, which was mainly affected by the rotation speed rather than the flow rate. To achieve the S of the same size, the length of the dynamic mixer was the shortest, and that of the SK static mixer was the longest. Moreover, to acquire the S of the same size, the dynamic mixer required the largest P, the SX static mixer needed a smaller P, and the SK static mixer required the minimum P.