The study reported here discusses the duration of the generalized tonic-clonic seizures (GTCS) among frontal lobe epilepsy (FLE), medial temporal lobe epilepsy (MTLE) and idiopathic generalized epilepsy (IGE).The study was done by analyzing the data from patients who had undergone video-EEG in 2009 and had GTCS during the monitoring. The patients were selected for the frontal lobe epilepsy (FLE), medial temporal lobe epilepsy (MTLE), and idiopathic generalized epilepsy (IGE). Once they met the criteria, the durations of all the phases were measured, then discussed if there were any difference in duration for different epilepsies.On comparison of the total duration of various types of seizures it was found that the duration of FLE (177 ± 212.6 sec.) was significantly different from the duration of MTLE (104.6 ± 51.8 sec.) and IGE (63.9 ± 28.2 sec.). It can be found in the comparison of GTCS that the duration of phase 6,7 of FLE (63.5 ± 30.9 sec.) was statistically significant compared with MTLE (37.3 ± 13.8 sec.) and IGE (46.4 ± 30.1 sec.). The duration of various types of epilepsy in the generalized tonic-clonic period was not statistically significant.Through this study, we found the differences of the duration of different types of epilepsies that provide the clinical basis for further studies of seizure mechanism and neural network conduction.