Aim: To explore the best startup time of controlling epilepsy with vagus nerve stimulation (VNS) and its effect through animal experiment, and observe the effect of VNS on electrocorticogram(EGoG) and electrical activity of hippocampal neurons in epileptic rats induced by kainic acid (KA). Methods: Adult healthy Wistar rats, weighed 220-250 g, were under intraperitoneal anesthesia with soluble pentobarbitone(40 g/L), then were injected subcutaneously KA(10 mg/kg, Sigma) for replication of epilepsia model. The left vagus nerves were stimulated with intermittent current pulses before and after seizures, The ECoG of frontal cortex and evoked discharges of CA1 area in hippocampus were recorded by silver ball electrode and metal microelectrode, respectively. Results: 1 The intensity and duration of ECoG were reduced, shortned and even disappeared completely in some cases by VNS with pulse of 3-4 mA, 33 Hz, 1 ms before seizures(F = 27.32, P < 0.001). The same stimulation was given when seizure reoccurred, it could only be reduced the degree but couldn't disappear completely. 2 The same stimulation was given when the burst discharges of CA1 in hippocampus induced by injecting subcutaneously KA appeared. The discharging frequency decreased, and continued to reduce 60 min and 120 min after stopping VNS (F = 8.531, P < 0.05). The result showed that if discontinuous VNS were given as early as possible, anti-epileptic effect was significant, and VNS could inhabit epileptic discharge of hippocampal neurons effectively. Conclusion: 1 The earlier VNS is used, the better the repression of seizure of epileptic models induced by KA is. 2 Anti-epileptic effect of discontinuous VNS on epileptic rats induced by KA, may be caused by continuous discharge of hippocampal neurons of CA1, which shows that hippocampal formation plays an important role in anti-epileptic effect of VNS.