In this paper, we address the problem of secure wireless information and power transfer in a large-scale multiple-input multiple-output (LS-MIMO) amplify-and-forward (AF) relaying system. The advantage of LS-MIMO relay is exploited to enhance wireless security, transmission rate and energy efficiency. In particular, the challenging issues incurred by short interception distance and long transfer distance are well addressed simultaneously. Under very practical assumptions, i.e., no eavesdropper's channel state information (CSI) and imperfect legitimate channel CSI, this paper investigates the impact of imperfect CSI, and obtains an explicit expression of the secrecy outage capacity in terms of transmit power and channel condition. Then, we propose an optimal power splitting scheme at the relay to maximize the secrecy outage capacity. Finally, our theoretical claims are validated by simulation results.