Abstract: An asymmetric model for the crosssection geometry of a intermeshing corotating asymmetric twinscrew extruder was proposed, and the mixing characteristics of it were analyzed by both experimental investigation and numerical simulation. The experimental characterization was conducted using an active nanometer CaCO3 filled PELLD with a novel corotating asymmetric twinscrew extruder and a traditional corotating twinscrew extruder, keeping a fixed output. Scanning electron microscope (SEM) micrographs revealed that nanoCaCO3 in the composites extruded by the novel corotating asymmetric twin screw extruder was more uniform with smaller particle sizes, and it showed an obvious toughening effect, which agreed with the numerical simulation results.