Supertough nylon 11 is prepared by using a plasticizer. The influence of plasticizers on the impact property and tensile properties of plasticized nylon 11 Were investigated. The results show that the impact strength is improved remarkably by methylbenzene sulfonamide, and the tensile strength is almost the same as that of natural-grade nylon 11. The study of the fracture morphology on plasticized supertough nylon 11 indicates that the fracture surface of plasticized supertough nylon 11 has a special feature, which is different from the fracture surface of general ductile polymer materials. It is similar to that of a multilayer distorted lamellar structure. There are many oriented fibrillar clusters on each layer, which are perpendicular to the impact direction. This was a new breaking phenomenon, which is found on supertough nylon 11. In regard to the experimental results, a "multilayer crack extension" mechanism is put forward. The fracture of supertough nylon 6 also verified this mechanism.