A new semantic pattern is proposed in this paper, which can be used by users to post questions and answers in user-interactive question answering (QA) system. The necessary procedures of using semantic pattern in a QA system are also presented, which include question structure analysis, pattern matching, pattern generation, pattern classification and answer extraction. A user interface of using semantic pattern is also implemented in our QA system, which allows users to effectively post and answer questions. It gains good overall user satisfaction.