The invention discloses an extendable markup language file editor, a method and a system for file transmission. The method comprises that: first data of a first XML file is replaced with an identifier according to the mapping relation to obtain a second XML file, the mapping relation is established according to a definition order and a definition identifier of the first data in the XML file; thenthe second XML file is transmitted; the identifier in the transmitted second XML file is restored by the first data according to the mapping relation to obtain the first XML file. Further for the second XML file, an instance document of an XML tree-shaped structure is made an encoding/decoding according to the depth search order of the tree and according to elements, element property, digital identifiers in a naming space and types of identified nodes before the transmission. The invention can largely reduce redundant loads to improve the occupation rate of the neat loads, further greatly improves the bandwidth utilization rate of the network and the transmission efficiency of the network.