in machine translation, long sentences are usually assumed to be difficult to treat. The main reason is the syntactic ambiguity which increases explosively as a sentence become longer. Especially, in the machine translation using sentence patterns, a long sentence causes a critical coverage problem. In this paper, we present a method of sentence partitioning which recognizes sub-sentence ranges by structure analysis, reducing the length of a sentence for translation. For the analysis of the clausal structure, phrase-level sentence patterns which have only a little syntactic ambiguities are employed. The structure analysis is conducted by the recognition of starting points of all clauses, dependency analysis, and depth analysis. Then, the ranges of sub-sentences are extracted based on the depth by stages. Our method was evaluated on 108 sentences extracted from CNN transcripts. It showed 85.2% accuracy in the detection of simple sentences.