Abstract: In order to reduce the complexity of the constraints between training sequences and improve the performance in amplify-and-forward (AF) twopath relay network, this paper proposes a signal transmission scheme based on precoding. In this new scheme, a pair of orthogonal precoding matrices are used to precode the signals at two relays, and the superimposed signals are separated by multiplying the corresponding decoding matrices at the destination. The new scheme can completely separate the two signals so that the original need to consider three training sequence design problems can be converted into two, which simplifies the complexity of training sequence design. Because the precoding scheme can compress the noise power and avoid the interference between two relay signals at the destination, the performance of single-path and two-path diversity combining bite error rate (BER) are improved. The simulation results verify the effectiveness of the new scheme.