A method of sharing network resource in a network system in which a first user device is able to access the Internet via a shared transport network and a first core network which is built or rent by a first tenant, a network sharing module being in communication between a controller and the first tenant, the method comprising steps of: receiving, by the network sharing module implemented on a calculation device, a first resource sharing request from the first tenant; requesting, by the network sharing module, the controller to determine whether the first resource sharing request is satisfied by a resource of the shared transport network, wherein the controller is configured to manage a plurality of forward devices in the shared transport network; generating, by the network sharing module, a first tenant identifier for the first tenant when the controller determines that the resource sharing request is satisfied by the resource of the shared transport network; transmitting, by the network sharing module, the first tenant identifier to the first tenant, wherein the first tenant returns at least one first group identifier and at least one first transport service type corresponding to each of the at least one first group identifier based on the first tenant identifier assigned by the network sharing module; requesting, by the network sharing module, the controller to generate at least one first packet header for the at least one first transport service type corresponding to the each of the at least one first group identifier; and requesting, by the network sharing module, the controller to update a plurality of flow tables of the plurality of forward devices according to the at least one first packet header, wherein data packets of the first user device are transmitted to the first core network through the shared transport network. receiving, by the network sharing module implemented on a calculation device, a first resource sharing request from the first tenant; requesting, by the network sharing module, the controller to determine whether the first resource sharing request is satisfied by a resource of the shared transport network, wherein the controller is configured to manage a plurality of forward devices in the shared transport network; generating, by the network sharing module, a first tenant identifier for the first tenant when the controller determines that the resource sharing request is satisfied by the resource of the shared transport network; transmitting, by the network sharing module, the first tenant identifier to the first tenant, wherein the first tenant returns at least one first group identifier and at least one first transport service type corresponding to each of the at least one first group identifier based on the first tenant identifier assigned by the network sharing module; requesting, by the network sharing module, the controller to generate at least one first packet header for the at least one first transport service type corresponding to the each of the at least one first group identifier; and requesting, by the network sharing module, the controller to update a plurality of flow tables of the plurality of forward devices according to the at least one first packet header, wherein data packets of the first user device are transmitted to the first core network through the shared transport network.