Some oxygen-containing groups, such as C-O-C, C-OH, C=O, C(=O)O, and C(=O)OH, were introduced onto linear low-density polyethylene (LLDPE) chains during ultraviolet irradiation under air, without adding any monomers and auxiliaries and without environmental pollution. After ultraviolet irradiation, the molecular weight of LLDPE decreased and its distribution became wider. The melting temperature and crystallinity of irradiated LLDPE decreased with irradiation time. The copolymer LLDPE-g-PA66 was formed by reaction between oxygen-containing groups of irradiated LLDPE and amine or carboxyl end groups and amide linkage of polyamide 66 (PA66) during preparation of PA66/irradiated LLDPE blends. Compared with PA66/LLDPE blend, the mechanical properties of PA66/irradiated LLDPE blends were improved greatly because of the improved interface interaction and dispersion.