This chapter focuses on the secure transmission of wireless-powered full-duplex (FD) relay systems, where a multiple-antenna source communicates with a single-antenna destination with the help of an FD relay in the presence of a single-antenna eavesdropper. It is assumed that the FD relay is wirelessly energy harvesting-enabled, adopting both transmit and receive antennas to harvest energy in time switching (TS) mode. As the objective of this chapter is to maximize the system secrecy rate by jointly designing the energy beamforming vector, the information beamforming vector, and the TS coefficient, an optimization problem is formulated in Sect. 6.2. The formulated problem is proven to be nonconvex, and the challenge is to concurrently solve out the three variables. To address this difficulty, an iterative algorithm is proposed in Sect. 6.3 to convert the formulated optimization problem into three convex subproblems, on which the closed-form solutions for the beamforming vectors are derived and the TS coefficient is obtained. The convergence property of the iterative method is analyzed. Simulations are performed in Sect. 6.4 to verify the theoretical derivations in terms of the convergence speed and the secrecy rate. The results reveal that the secrecy rate performance of exploiting the transmit antenna together with the receive antenna for energy harvesting at the FD relay outperforms that of only the receive antenna case. Moreover, although loopback interference exists between the antennas, FD relaying can substantially increase the secrecy rate compared with the half-duplex relaying architecture. Section 6.5 concludes the work.