We applied event-related potentials (ERPs) to assess brain activities with inhibition of irrelevant conflict information processing during visual selective attention. Fifteen healthy subjects matched two sequentially presented color spots (S1 and S2) in a visual selective attention task. The two spots might be presented in a fixed position of either the same color (match), or different colors (color conflict). They might be in different positions of the same color (position conflict), or different colors (color and position conjunction conflicts). Subjects matched the stimuli in two different sessions according to different attention tasks: attending to color (Ac) or attending to position (Ap). In the time window of 201-350 ms after the onset of S2, an ERP component the N270, was elicited in all the conflict conditions with the amplitude enhanced in the task-relevant conflict. The amplitude of the N270 in the conjunction conflict condition was lower than that of the task-relevant conflict condition in either Ac or Ap session. The results suggest that the conflict processing is modulated by attention. All kinds of conflicts might be processed in a common system in the human brain, the conflict processing system. Due to the limited capacity of the conflict processing system, the decrement of the N270 in the conjunction conflict condition is deduced to reflect an active inhibition for the processing of the irrelevant conflict.