Polyamide 6 (PA6) is one of the most commonly used engineering plastics due to its high mechanical characteristics. However, PA6 has poor ductility that limits the performance in some applications. To improve its ductility, elastomeric polyrotaxane (PR) with cyclodextrin (CD) as cyclic molecule was used. With the sliding effect of CD along backbone, the enhancement of ductility of PA6 is extremely expected. The purpose of this research is to develop a novel blending technology by using octa-screw extruder for PA6/PR alloy. Two types of PR with different molecular weight were used. PA6/PR alloy with a ratio of PA6/PR=98/2 wt% was prepared under rotation speed of 100 rpm at 230 ℃. Dispersion of PR in PA6 matrix was observed by scanning electron microscope (SEM). PA6/PR alloy test pieces for mechanical test were prepared by using injection molding. The mechanical properties were carried out by tensile test (low-speed test: 5 and 500 mm/min, high-speed: 60,000 and 120,000 mm/min), bending test, and impact test. SEM images revealed that PR domains with 50 to 100 nm show a good dispersibility in PA6 matrix. In tensile test, PA6/PR alloy showed excellent ductile behavior. It was found that by increasing tensile speed has the result in reducing yield stress. At low-speed test, there was no molecular weight dependency of PR on ductility. The enhancement in ductility of PA6/PR alloy is due to physical crosslinking between PA6 and PR. Crosslinking points move freely because of the sliding effect of CD. In addition PR increased break elongation of PA6/PR in high speed (60,000 mm/min), while decreased break elongation PA6/PR compared with neat PA6 in low speed test (5 mm/min). The octa-screw extruder can effectively enhance mixing ability by increasing shearing time of PA6 and PR.