On Subtitle Translation of Chinese Costume Drama, The Longest Day in Chang’an

China’s enhanced international influence creates a good environment for spreading its traditional culture overseas. In recent years, Chinese subtitle translation is no longer restricted to translating foreign works into Chinese, with costume drama subtitle translation gaining more and more attention. However, relevant research in China is inadequate, and differences between Chinese and English aggravate this difficulty, which may be solved by studying and analyzing the subtitle translation of The Longest Day in Chang'an under the guidance of Nida's functional equivalence theory from the perspectives of lexical equivalence, syntactic equivalence, and stylistic equivalence, so as to provide the guidance to translators to render a proper translation both in the conveying of information as well as ensuring readers' response.