In this letter, we investigate the secrecy performance of the simultaneous wireless information and power transfer (SWIPT) system over generalized-K fading channels. After analyzing the communications scenario, we derive the closed-form expression for the secrecy outage probability (SOP), and give some simplified expressions for SOP in some special cases. Effective secrecy throughput is also investigated to capture the amount of secure transmitted information. To derive the diversity order, the asymptotic SOP is also analyzed when the average signal-to-noise ratio is large sufficiently. Finally, numerical results are used to validate the correctness of our derived expressions.