Animals play an indispensable role in the history of human development. Not only have they been deeply affecting human life, but also changing the use of our languages. The similarities and differences between new and old words reflect the changing roles and fixations of animal cultures in human life. If we consider the types of animals that are intimate to humans in modern times, "cats" and "dogs" are particularly the main ones. Therefore, the author takes the rhetorical transformation of "cat" and "dog" as the research angle and collects the relevant corpus on the title of PTT to sort out and analyze from the six aspects : (1) Familiar Words, (2) the gendered, (3) the animal instinct, (4) the social value of pet "things", (5) the praise and disdain between cats and dogs, and (6) Anthropocentrism,(7)cultural differences in foreign languages.