The invention discloses a routing method of an optical transport network OTN, comprising the following steps: getting the topology structure of an optical transport network OTN, and determining the number of switching nodes contained in the OTN, the number of OTN switches contained in each switching node and the connection relationship between the switching nodes; determining the shortest paths between each switching node and the other switching nodes based on the number of OTN switches contained in each switching node, the connection relationship between the switching nodes and the connection relationship between the ports inside each switching node; randomly generating test data sent by each switching node to the other switching nodes, and determining the communication traffic sent by each switching node to the other switching nodes based on the corresponding relationship between the bandwidth of test data and the communication traffic; and determining the route between each switching node and the other switching nodes in the OTN based on the communication traffic sent by each switching node to the other switching nodes, the shortest paths between each switching node and the other switching nodes and a default maximum traffic of the paths.