Based on Wang Jianguo’s translation theory, this paper takes the subtitle translation of the television series Dune: Prophecy as a case study to explore the ―expansion strategy‖ in English–Chinese translation and its applications. The study shows that, compared with the ―compression‖ strategy typically discussed in Chinese–English translation, English–Chinese translation often requires expansion at the levels of language and cognition through semantic explicitation, logical cohesion, and cultural adaptation. The case analysis demonstrates that an awareness of expansion is reflected in the blurring of boundaries among cognitive semantics, structural form, and pragmatic rhetoric. Its core lies in reconstructing context and making logic explicit so as to balance the fluency of the target text with depth of meaning, thereby enhancing Chinese viewers’ comprehension of and emotional engagement with the plot. This study provides a theoretical reference for audiovisual translation practice and reveals the impact of expansion strategies on the aesthetic effect and communicative efficacy of translated subtitles in cross-cultural contexts.