Objective:To compare the difference of epileptiform discharges detection in patients with epilepsy between the 25 electrodes electroencephalogram (EEG) system proposed by the International Federation of Clinical Neurophysiology in 2017 and the previous 19 electrodes EEG system.Methods:Patients suspected of epilepsy or with confirmed epilepsy who need a follow-up EEG were collected in Zhongshan Hospital, Fudan University from March 2018 to November 2019, and conventional video-EEG recording was performed on all patients for two hours with the standard 25 electrodes EEG system. Two neurophysiologists reviewed the recordings blindly using the 19 electrodes system and the 25 electrodes system, marking the epileptiform discharges and their amplitudes. Finally, the data were statistically analyzed.Results:A total of 403 patients were included in the study, in which 263 cases were diagnosed as epilepsy, including 129 cases of generalized epilepsy, 115 cases of temporal lobe epilepsy, 13 cases of frontal lobe epilepsy, two cases of parietal lobe epilepsy and four cases of occipital lobe epilepsy. In 115 temporal lobe epilepsy patients, 76 (66.09%) and 100 (86.96%) records were detected epileptiform discharges by the 19 or 25 electrodes EEG system respectively, and the difference was statistically significant (χ2=13.939, P<0.001). While in patients with non-temporal lobe epilepsy, there was not statistically significant difference between the two systems. In 76 patients whose temporal epileptiform discharges were detected by the two systems, the amplitudes of epileptiform discharges in the newly-added inferior temporal electrodes (F9/F10, T9/T10, P9/P10) and the original temporal electrodes (F7/F8, T7/T8, P7/P8) were (61.53±22.64) μV and (48.25±20.90) μV, respectively, with statistically significant difference between the two groups ( t=5.486, P<0.001). In patients with abnormal [79.59% (39/49) vs 61.22% (30/49), χ2=3.967, P=0.046] and normal [95.45% (42/44) vs 70.45% (31/44), χ2=9.724, P=0.003] imaging, the ability of the 25 electrodes EEG system to detect epileptiform discharges was higher than that of the 19 electrodes EEG system. Conclusion:The 25 electrodes EEG system can significantly improve the detection ability of temporal epileptiform discharges in patients with epilepsy, which is recommended for regular use to increase the detection ability of temporal area abnormal wave and assist the diagnosis and treatment of epilepsy.