Understanding the initiation site and propagation of epileptiform discharges are of important significance for investigating the mechanisms of epilepsy and thereby for the clinically remedy. In order to solve the above problems, epileptiform discharges induced by low-Mg2+ artificial cerebrospinal fluid (ACSF) in Sprague- Dawley (SD) rat hippocampal slices were recorded by microelectrode array. Two components of epileptiform discharges: field potentials and multiple unit activity (MUA) were analyzed. Firstly, the onset time of field potentials in stratum pyramidale was calculated and compared to locate the initiation site and propagation of epileptiform discharges. Then cross-correlation analysis was applied to spike trains of MUA. Time delays obtained from cross-correlation function further confirmed the initiation site and propagation of epileptiform discharges in the whole hippocampal slice. The results revealed that epileptiform discharges in CA3 had larger amplitudes and longer duration than that in CA1, which indicated more excitability in CA3. Field potentials as well as MUA in CA3b occurred earlier compared with the synchronous signals in CA3c and CA1. The time delays between the onset and its following areas were positive relative to the distances between them. The result demonstrated that in low-Mg²⁺ ACSF-perfused SD rat hippocampal slice, epileptiform discharges originated from CA3b and propagated to CA3c and CA1 region respectively.