Abstract: Clause-clause interlingua transformation mechanism refers to the equivalent transformation of word to word, phrase to phrase, and clause to clause, including both literal and free translation. When a clause in the source text is transformed into that in the target text, literal translation based on the direct transforming of the whole structure is seldom used, while the free translation is frequently employed, which involves amplification, omission, shift of perspectives, division and combination of propositional elements.