Event-related potential (ERP) was used to examine the interactions between working memory and selective attention. We combined two unrelated tasks, one requiring working memory and the other selective attention, which were performed by some undergraduates. The ERP results revealed that both congruent and incongruent stimuli in the selective attention task evoked an N400 component, reaching the peak point at around 500 ms. The N400 evoked by incongruent stimuli was more negative than that of congruent, which indicated the difference of semantic N400. Furthermore, working memory load had a significant influence on the N400 evoked by selective attention task in parietal region. And working memory load showed difference in the ERPs of working memory retrieval in central and parietal regions. The ERPs of probe under high working memory load were more positive from 350 to 550 ms post-stimulus; however, stimulus type of selective attention had no influence on working memory retrieval. The present study shows that working memory does not play a major role in the selective attention, especially in ignoring distracter, but it influences the performance of the selective attention as the background. The congruency of target and distracter in the selective attention task does not influence the working memory retrieval.working memory, selective attention, N400Working memory (WM) and selective attention are cognitive constructs central to the dynamic interplay between perception, thought and action [1] . An essential feature of WM is the on-line maintenance of information to guide future behavior. And visual selective attention can give task-relevant information higher priority in perception, decision, and response operations in face of distracting information.Studies of visual attention and WM showed that, the activation in frontal cortex was associated with attention processing [2,3] , while the information maintenance in WM was modulated by some specific areas in parietal cortex [4,5] . Despite a great deal of researches on visual attention and WM, the details of their relationship have been exploring only recently.Some researchers claimed that WM might play a certain role in the control of selective attention [6,7] . But opinions on this issue were diverse. Some proposed that a high WM load should result in greater processing of irrelevant distracters, and there showed a direct causal role for WM in the control of selective attention [6,7] . de Fockert and his colleagues [7] examined this issue. They flashed the names of some pop stars and politicians on a screen in front of the participants, asking them to choose the profession of each name. As each name appeared on the screen, the researchers also showed a picture of a face that might or might not match the name. This forced the participants to try to ignore the faces and focus on the words. As expected from their previous work, the participants took longer time to answer when the face did not match the name than when it did. At the same time, to investigate the involveme...