This article reveals the importance of language in communication between government and the public by reviewing Federal Plain Language Guidelines. On this basis, this paper argues that governmental language competence includes three dimensions: language category, language carrier and language quality. In handling of public affairs, there is need to strengthen language emergency construction and enhance the language capacity for serving special groups. Also, it is necessary to construct training mechanism for general and specific governmental language competence according to functions of government departments, and to develop detailed regulations for implementation.