The present invention relates to the field of traffic, especially to a maximum entropy method used for traffic subnetwork trip matrix estimation. The method comprises the following steps of: S1: selecting and establishing an abstracted sub traffic network, wherein the network is formed by a node set N and a road section set A, and the N comprises a starting point set R and a terminal point set S;S2: establishing and solving the maximum entropy model of a traffic subnetwork trip matrix; S3, in the abstracted sub traffic network, employing the maximum entropy model, performing initialization toobtain a feasible solution of the maximum entropy model, designing an algorithm to find and solve a current solution decreasing direction of decreasing of a target function value of the maximum entropy model; S4: performing linear search, performing solution, determining an optimal [Alpha], and determining the optimal step of the decreasing; S5: updating the feasible solution; and S6, allowing the algorithm to end the examination. The maximum entropy method used for the traffic subnetwork trip matrix estimation takes easily obtained flow of each road section of the whole network as unique input of the model to establish the maximum entropy problem so as to improve the algorithm efficiency, allow the method to be utilized in a large network and improve the prediction precision. The maximumentropy method used for the traffic subnetwork trip matrix estimation can be used for assessment of influences of different network changes on the subnetwork flow.