Abstract: In order to reveal the electroencephalogram (EEG) differences between truth and lying, the event related synchronization (ERS) is deeply studied for spontaneous EEG during the lying detection experiment. The ERS corresponding to delta and theta rhythm of EEG is analyzed in detail. The results indicate that ERS corresponding to delta and theta rhythm can reflect the deception-related psychological states. The delta synchronization is strongly related with P300. The theta synchronization effect overlaps with the ERPs effect, but ERPs and the synchronization effects have different scalp distribution character. The results show that the theta synchronization effect is strongest in Fz electrode and the ERPs effect is maximal on Pz electrode. This evidence implies that ERS corresponding to theta rhythm and P300 might reflect the deception-related cognitive psychological process from different aspects.