Based on Bakhtin’s polyphony theory, this dissertation intends to probe Moby Dick from themes, structures and the genres. A holistic study of polyphony in Moby Dick offers a dynamic and full perception of the novel. Within the context of the polyphony theory, the novel presents multiple levels and dimensions in interpretation. The polyphony of themes deals with the polyphony of characters including Ahab and the white whale, the dialogic relationship between the land and the sea and between the civilized and the savage. There are contradictory features coexistent in characters like Ahab and Moby Dick, which enrich their personalities and elevate them from flat characters to round characters. In Moby Dick, with the application of polyphony theory, the antagonism between the land and the sea, and the civilized and the savage reveal a dynamic confrontation against each other. Within themselves, each displays an indefinite contradiction in its essence. In this way, exploring the polyphony of the themes provides new enlightenment and inspiration to the underlying meanings of the novel. The polyphony of structures refers to the coexistence and interaction among the nonnarrative chapters, as well as between the non-narrative parts and the narrative parts. The Etymology offers the dictionary meanings of whales. The Extracts give the literary presentation of whales in all kinds of discourses. The cetological chapters offer the meaning of whales in texts. They are philological basis, formal addition and thematic echoes of narrative parts. They are crucial in building the meanings of whale, delivering the themes and messages, and forming an interaction in structures and genres. The creation and full use of the non-narrative parts in the novel are Melville’s special writing strategy. This dissertation studies the dictionary genre, the religious genre and the dramatic genre. The dictionary genre offers an authoritative definition which establishes an objective and authentic basis on the novel. The religious writings have serious, solemn and purifying effects to the pulpit and readers. The dramatic genre allows characters to express their genuine feelings and emotions in a free and genuine manner, hence shortening the distance between characters and readers. The dramatic flow of emotion moderates the atmosphere of scenes and intensifies the dramatic conflicts, helping to build the plot and themes of the novel. The polyphony of genres provides diversity in the styles and tones of the novel. The polyphony of genres moderates the tempo, distance and focus of narration, helping to push the plot and the climax of the novel and creating a dynamic perception in reading the novel.