Visual search task was used to explore the role of facial identity in the processing of facial expression. Participants were asked to search for a happy or sad face in a crowd of emotional face pictures. Expression search was more quickly and accurate when all the faces in a display belonged to one identity than two identities. This suggested the interference of identity variance on expression recognition. At the same time the search speed for a certain expression also depended on the number of facial identities. When faces in a display belonged to one identity, a sad face among happy faces could be found more quickly than a happy face among sad faces; otherwise, when faces in a display belonged to two identities, a happy face could be found more quickly than a sad face.