Abstract: This application provides a method and system of evidence preservation for digital documents. The method comprises: converting, by a client, the digital document to a document code, which is uniquely corresponding to the digital document; uploading, from the client, the document code and first attribute information of the client to a server, wherein the first attribute information includes user information and geographical position information of the client; and incorporating, by the server, second attribute information into the document code and the first attribute information to form a code file, and preserving the code file in a code file database of the server, wherein the second attribute information includes time information indicating when the document code is received by the server; wherein when contents of the digital document are changed, contents of the document code are changed accordingly.