Polyethylene terephthalate (PET) has been widely used as fiber, film and plastic products owning to its good properties such as chemicals and heat resistance, anti-creep, relatively low price, and easy recovery. In particular, in order to broaden the application field of PET, CPET features higher crystallinity, shorter processing cycle and higher heat-resisting temperature than PET has been explored widely. In this paper, three methods were employed and compared to improve the heat resistance of PET, including inducing crystallization (three kinds of nucleating agent), chain extension reaction (two kinds of chain extender) and blending modification (two kinds of blending polymer). Compared with inducing crystallization, either chain extension reaction or blending modification improved the heat resistance more significantly. The optimal nucleating agent, chain extender and blending polymer is TiO2 (Rutile, inorganic nucleating agent), epoxy type chain extension agent and nylon 66, respectively. Considering the truth that three methods play roles according to different mechanisms, a kind of PET composite material enduring temperature as high as 240℃ is obtained through the synergistic effect of the three modified methods.