The paper gives a survey on three approaches of statistical machine translation and the evaluation methods used in smt , the basic idea of parallel grammar based approach is to build parallel grammars for source and target languages , which conform the same probabilistic distribution 摘要本文綜述了基于信源通道思想和基于最大熵思想的統計機器翻譯方法并介紹了統計機器翻譯的評測方法。