The invention relates to a method for reducing network coding cost, belonging to the technical field of communication. The method comprises the following steps: establishing path clusters from an information source node to each information sink node in a distribution way; acquiring the path cluster bandwidth of each path cluster; determining the multicasting maximum flow bandwidth of the information source node according to the path cluster bandwidth; trimming the path clusters with the path cluster bandwidth more than the multicasting maximum flow bandwidth; and determining nodes of a multicasting transport topology and nodes which participate network coding. The invention also provides a device and a system for reducing the network coding cost. The embodiment of the invention decreases nodes containing codes by trimming an established transport route, thereby reducing the network coding cost.