With the deepening of cross-cultural communication, film has gradually become one of the important media in the field of mass communication. Subtitle translation, as a special form of literary translation, is also a medium to eliminate language barriers and promote cultural transmission, which plays an indispensable role in the promotion of films. This paper starts with the characteristics of film subtitle translation and discusses the guiding role of functional equivalence theory in film subtitle translation from the aspects of language, social structure, and ideology through analyzing the translation example of Homeless to Harvard: The Liz Murray Story, so as to make the cultural characteristics and language styles of the source language films obtain the maximum creative representation.