1. A method of text alignment of a first document and a second document that is a translation version of the first document, comprising: accessing a first text of the first document and a second text of the second document, wherein the first and second texts include at least one paragraph; dividing the first text and second text into sub-sentential segments, wherein each of the sub-sentential segments is considered as a word and the length of each sub-sentential segments is the number of words contained therein; obtaining pairs of alignment units from the first text and the second text after the sub-sentential segment processing, wherein each of the alignment units includes at least one sub-sentential segment; and aligning and scoring the pairs of alignment units.