Abstract： Background Prior research about N400 has been mainly based on English stimuli,while the cognitive.processing of Chinese characters is still unclear.The aim of the present study was to further investigate the semantic processing of Chinese idioms.Methods Event related potentials (ERP) component N400 was elicited by 38 pairs of matching (congruent) and mismatching (incongruent) ended Chinese idioms:ending words with same phoneme but different shape and meaning (sPdSdM),with similar shape but different phoneme and meaning(sSdPdM),with same meaning but different phoneme and shape(sMdPdS),and words with different phoneme,shape and meaning(dPdSdM)and recorded by Guangzhou Runjie WJ-1 ERP instruments.In 62 right-handed healthy adults(age 19-50 years),N400 amplitudes and latencies were compared between matching and mismatching conditions at Fz,Cz and Pz.Results N400 showed a midline distribution and could be elicited in electrodes Fz, Cz and Pz.The mean values of N400 latencies and amplitudes were obtained for matching and mismatching ending werds in healthy adults.Significant differences were found in N400 latencies and amplitudes in matching and mismatching ending-werds idioms in healthy adults(P<0.05).Compared with matching ending-werds jdioms, N400 latencies were prolonged and the amplitudes were increased in mismatching ones.N400s elicited by different types of stimuli showed different latencies and amplitudes.and longest N400 latency and largest N400 amplitude were elicited by ending-werds with dPdSdM.No gender difference was found of N400 latency and amplitude in this study (P>0.05).Conclusions Compared with English stimuli.Chinese ideographic words could provide more flexible stimuli for N400 research in that the werds have 3-dimension changes-phoneme.shape and meaning.Features of N400 elicited by matching and mismatching ending words in Chinese idioms are mainly determined by the meaning of the werd.Some issues of N400 elicited by Chinese characters deserve further research.