The present invention discloses an OTN circuit routing method and a system. The method comprise the steps of converting the network element information of all original networks into network element codes in the binary system; comparing each field of the network element codes at the initial end of a to-be-established routing with each field of the network element codes at the terminal end of the to-be-established routing, judging whether the fields of the network element codes at the initial end and the terminal end of the to-be-established routing are the same or not, determining the hierarchy of the required routing according to different fields of the network element codes at the initial end and the terminal end of the to-be-established routing, and successively routing the backbone layer, the convergence layer and the access layer of a network from top to bottom; acquiring cluster nodes at the initial end and the terminal end according to the network element codes, and establishing the routing of each layer of the network based the cluster codes; and finally splicing up the already established routings of all layers of the network to form the complete routing. According to the technical scheme of the invention, the automatic routing and path-finding function of an OTN circuit in the cross-manufacturer, cross-region, cross-level and end-to-end manner can be realized. Meanwhile, the automation degree and the accuracy of the circuit debugging operation are improved. Moreover, the error rate and the configuration time of the routing operation through the manually searching and computing process can be reduced.