Werner Koller devoted a great deal of research on equivalence theory. According to hisequivalence theory, there are five aspects of equivalence. Among them, denotativeequivalence has to do with the equivalence between target text and source text’s referential ordenotative meanings. It refers to that the source text and the target text have the samedenotations, in other words to say, they convey the same linguistic facts; connotativeequivalence has to do with the lexical choices from the perspective of the lexis containingemotions, feelings and the like; text normative is related to Reiss’s text type theory, i.e.,expressive type, informative type and appellative type. Among them, essay belongs to theexpressive text.