Abstract. Cyclic olefin copolymer (COC) consists of a random copolymer of ethylene and norbornene, it has excellent properties, such as non-crystalline, high transparency, chemical resistance, etc. However the impact strength need be improved for packaging and medical materials. The study is presented of increasing the toughness of COC with impact modifiers consist of thermoplastic elastomers by mixer, the impact strength was improved to applicable environment. The microstructure of modified COC was observed by a scanning electron microscope (SEM), it is shown that the blend system was spherical and dispersed well, and the diameter of impact modifiers was 0.74 ìm. Although the tensile strength of modified COC was decreased slightly, the impact strength (4.3 KJ/m2) was increased significantly at normal temperature with tensile and impact testing machine. The toughness of modified COC was improved; it could be used for storage application. Keywords: Cyclic olefin copolymer; Thermoplastic elastomers; Toughness; Impact strength