The KEK Linac injects the electron and positron beams into the KEKB-LER, KEKB-HER, PF and PF-AR rings with four different characteristics. In order to improve the beam operation efficiency, we have planned the simultaneous top-up operation for the PF and KEKB. The fast beam switching mechanisms are being developed and installed. For those mechanisms, the linac parameters of timing and low-level rf phase should be controlled in the pulse by pulse of 50 Hz. In this paper, we will present the event timing system to the KEK Linac control system in detail.