This paper considers a physical layer se-curity model in wireless communications.Two legit-imate users communicate through several relays with the presence of an eavesdropper.We jointly design the relay beamforming weights and minimize the to-tal relay transmit power,while ensuring users\' Qual-ity of Services and preventing the information being eavesdropped at the same time.The problem is a robust optimization problem,because of the imper-fect channel state information from users and relays to the eavesdropper.First the original problem is sim-plified,where the high order robust terms are omit-ted.Then we design an iterative algorithm based on line search,by solving two Quadratically Con-strained Quadratic Programming subproblems and a one-dimensional subproblem.Simulation results indi-cate that the proposed algorithm outperforms the state of the arts.