Embodiments of the present invention disclose a path determining method, apparatus, and system. In a hybrid network including one controller for implementing a control function, the controller may separately obtain network topology information of a first network and a second network of different network types by using a same control channel protocol. When the controller obtains a path determining requirement for the data transmission path, because the controller has the network topology information of the first network and the second network, during computation of the data transmission path, the controller can determine a path computation result including transmission path parts of the first network and the second network, without performing additional information exchange with another device, and send the path computation result to the first network device. In this way, planning efficiency of the data transmission path is improved.