Provided are an automatic speech translation system and a method for obtaining accurate translation performance with a simple structure. Because input and output sentences are written in different languages, automatic speech translation requires techniques for processing different languages. Repetition of text processing like morpheme analysis or sentence parsing in conventional automatic speech translation can complicate the overall translation process. Meanwhile, although input and output sentences are written in different languages, they have to have the same meaning and a corresponding sentence form and words. Accordingly, the corresponding words and sentence forms of the two languages can be expressed with a simple structure and utilized in the automatic speech translation process, thereby maintaining consistency during the process and avoiding unnecessary process repetition, which reduces errors and improves performance.