The invention discloses a data double-path backup transmission method for a software-defined network. The data double-path backup transmission method comprises a path planning process and a dual-path forwarding process, which are centralized. The method comprises the steps that: an SND network manager allocates two links with the least overlapped nodes to a service flow having double-path backup transmission demands according to entire network topology and sends the allocation result to each switch node on the path in the form of a forwarding flow table. A network switch forwards the service flow according to flow table entries: a starting end switch receives user data and copies and respectively ends the user data to two downstream switches according to the flow table entries; an intermediate switch forwards the data according to the flow table entries, and a tail end switch polymerizes and sends the received data to a terminal user. According to the data double-path backup transmission method disclosed by the invention, the two links having the smallest overlap ratio in the network is used for transmitting data, so as to maximally avoid data loss caused by the failure of a certain node or a certain link in the network and improve the transmission reliability of critical services.