To solve the multicommodity flow problem in traffic network, this paper analyses the multicommodity flow traffic network with same cost, and builds the composite parameters and composite indicators on account of the successive shortest path algorithm and the Ford-Fulkerson algorithm. Based on the corresponding calculation rules of composite parameters and composite indicators, this paper builds a minimum cost flow algorithm for multicommodity flow traffic network and the feasibility of this algorithm is verified by an example. This algorithm provides the basis to solve the problem of multicommodity flow minimum cost flow with same cost which is quite widespread in the field of transportation.