The invention discloses a dynamic allocation method of coding vector based on graph coloring in a multicast network. Coding vectors are allocated for the multicast network based on network coding, that target node receives global coding vector linearity is not related is guaranteed. Based on the purpose, the invention provides a coding vector allocation method based on graph coloring, the method comprises the following steps of: converting a multicast tree needing allocation coding vector into a line graph, then dividing the line graph into different areas for constructing simple planar graph,next, mapping different colors into different coding vectors which are allocated to each top point of the areas (namely each edge of the multicast tree). After the global coding vectors are allocatedfor all the edges of the multicast tree, a source node is needed to record original coding vectors, the target node records decoding matrix, and the coding node calculates and records local coding vectors. During the transmission of data, the source node and the coding node need to transmit linear combination of information vectors and coding vectors downward; and the target node calls the decoding matrix and adopts a Gaussian elimination method for decoding.