Facing the new wave of Artificial Intelligence brought by deep learning and big data, the perception AI has been changing the interaction between humanity and the world completely. When bioengineering, cybernetics and computer science are trying to stealthily erase the boundary between humans and nonhumans, the theoretical circle changes accordingly--posthumanism, which aims to deconstruct the anthropocentrism, comes into being. Meanwhile, as a perfect combination of modern technology and art, science fiction films are at the front line of reflecting the thought of man-machine relationship in posthumanism. Therefore, based on the close relationship among artificial intelligence, posthumanism and science fiction films, this paper selects Ex Machina released in 2014 as the representative of many artificial intelligence films. Through the combination of literature analysis and case study, this paper analyzes the man-machine relationship in this film from the perspective of posthumanism, and in connection with the current situation of artificial intelligence, explores the blueprint for the coexistence of human beings and artificial intelligence in the future.