The invention discloses a method and a device for determining a transmission path, and aims to solve the problem that a way of allocating a transmission path to data needing to be transmitted by a terminal in a conventional network is not suitable for a SoftNet network. The method comprises the following steps: receiving a request message transmitted by a terminal, wherein the request message is used for requesting establishment of a forwarding path for data to be transmitted of the terminal; determining all available paths capable of forwarding the data of the terminal according to a network topological structure; and allocating transmission rates to all the available paths, and transmitting the transmission rates of all the available paths to switches on all the available paths, so that the switches forward the data to be transmitted according to the allocated transmission rates.