The complex sentence structure and complicated semantic logic of English long sentences are the difficult points that need to be overcome urgently in English translation. This paper outlines the basic direction of machine translation based on the perspective of translation purpose. Based on the grammatical categories of English words, lexical annotation is completed, and regular expressions for matching English long sentences are proposed based on the annotation results. After realizing the preprocessing of English text, the features of the text are extracted and converted into the format required by the CRF model, and the long-sentence slicing is completed through the training of CRF. The cut Encoder encoding and Decoder decoding were utilized to generate the final machine translation result. In the test of the United Nations machine translation corpus, this paper’s method improves the translation performance in the English-Chinese direction by 0.29 Bleu value and the translation performance in the Chinese-English direction by 0.13 Bleu value compared with the method of Xu and Zens. The translation performance is effectively improved by combining long sentence slice translation with modal analysis.