A network controlling method and a network controller are provided. The network controlling method includes the following steps. A hybrid SDN-Ethernet system including a plurality of hosts, a plurality of Ethernet switches and m Software-defined networking switches (SDN switches) is provided. m is larger than or equal to 1. A first path according to at least one default spanning tree in the hybrid SDN-Ethernet system is obtained. m×k optional paths are obtained. Each of the m SDN switches is set as a beginning of each of k of the m×k optional paths. A second path is selected according to the m×k optional paths and the first path of the at least one default spanning tree.