Twenty Thousand Miles Under the Sea was a science fiction novel by Verne. The novel mainly tells the story of a submarine led by the scientist Nimo de Montesi to explore the deep sea. The theme of the novel could be considered from many angles, the most important of which was the significance of scientific exploration and human civilization. Through describing the ecological environment of the seabed and the discovery of underwater cultural relics, the novel shows in-depth study and awe of the natural world. At the same time, the novel also presented the understanding and reflection of human civilization, especially the impact of the development of science and technology on human society. Through the exploration of submarines, Nimo de Montesi discovered that the deep sea contained huge wealth and the achievements of human civilization, but he also discovered the huge potential of technology and the possible disasters. Therefore, the theme of " 20,000 Miles Under the Sea " could be summarized as the significance of scientific exploration and human civilization, as well as the impact of technological development on human society.