Metadata is a critical aspect of describing, managing and sharing museum data. It is challenging to develop a general standard that will meet the requirements of different museums due to the large range of data types. The capability of concise description and the simplicity of use need to be considered. In this paper, we report on a finished project that aims to design the metadata for museum in China. An extensible metadata standard based on Dublin Core is presented, which includes a core metadata, extension rules and specific metadata. For the core metadata, we introduce the terms, definitions, registration rules and detailed examples of description. The principle of choosing the terms and refinements is discussed. A specific metadata for porcelain is discussed as an extension example.