The invention discloses a physical layer secure transmission method for a single-antenna amplification forwarding relay network. The method comprises a first phase that a source node sends secret information to all relay nodes, and moreover, an interference node sends interference signals to a destination node, an eavesdropping node and all relay nodes, thereby protecting currently transmitted information; and a second phase that each relay node multiplies signals received in the first phase through adoption of diagonal element values of a precoding matrix and then forwards the signals, wherein the precoding matrix is a diagonal matrix, diagonal elements are relay node cooperative beam former weighting coefficients, and moreover, the interference node continues to send the interference signals to the destination node and the eavesdropping node, under the power constraint of the source node, the relay nodes and the interference node, the power distribution of the source node and the relay node cooperative beam formers are optimized, and the maximum secure rate of the single-antenna amplification forwarding relay network is solved.