People often need to find documents that previously saved on their mobile phones. When searching a document, sometimes people cannot recall the exact name of it, but can remember some objects in it, such as the figures, tables or formulas in the documents, the source of the documents, or related topics. And the existing mobile phone document management software cannot associate the content of the document with itself. Therefore, how to extract document information into attributes tags to associate them with documents and how to re-find the expected documents based on these tags are practical and valuable. This paper proposes a method for re-finding mobile phone documents based on feature knowledge graph. First, we use four features to describe the documents and extract tags to form attributes. Then we link the attributes with the documents to form the document knowledge graph and propose a calculation algorithm of the four tags' weight. Finally, we propose the sorting and re-finding method based on the feature knowledge graph. By using personal mobile phones data, the experiment results verify the effectiveness and efficiency of this method.