The traditional digital image correlation method is difficult to measu re polymer materials deformation directly because of its low correlation.The measurement of large deformation is a significant problem for engineering.In this paper,we propose a modified digital image correlation method to measure th e large deformation in the whole process of polymer materials.Firstly,a kind of initial matching metho d based on multiple core points is proposed to improve the matching points on the robustness and efficiency;then,a modified dig ital image correlation method,which can improve the correlation based on multiple benchmark matching method,is introduced;Finally, according to the above key technology research,the large deformation measurement system is developed to measure large deformation of density polyethylene by the uniaxial tensile test.Experime ntal results show that the method can realize real time,dynamic,full field measurement of greater than 500% strai n distribution of the polymer materials deformation states.The method provides an effective non-contact measurement way and has high practical value in engineering.Th e measurement of large deformation has the vital significance especially for new materials research in mechanical properties.