Community-based question answer (Q&A) has become an important issue due to the pop- ularity of Q&A archives on the web. This pa- per is concerned with the problem of ques- tion retrieval. Question retrieval in Q&A archives aims to find historical questions that are semantically equivalent or relevant to the queried questions. In this paper, we propose a novel phrase-based translation model for question retrieval. Compared to the traditional word-based translation models, the phrase- based translation model is more effective be- cause it captures contextual information in modeling the translation of phrases as a whole, rather than translating single words in isola- tion. Experiments conducted on real Q&A data demonstrate that our proposed phrase- based translation model significantly outper- forms the state-of-the-art word-based transla- tion model.