The human face is an object most frequently viewed by humans and thus, human face recognition is such a familiar part of everyday life. Face recognition includes familiar face recognition and unfamiliar face recognition. The difference between the two kinds of recognition has been proved. Familiar faces were recognized more quickly and accurately than unfamiliar faces. The neurophysiologic study has found that there are different activation brain region between familiar and unfamiliar faces recognition. Comparing to recognition unfamiliar face, recognition familiar face can activate more region. They are the bilateral prefrontal, lateral temporal, hippocampus gyri, amygdala，posterior cingulated cortex and lower right frontal. There is the difference of the event-related potentials, including N400 and P600. Many factors affect face recognition, external features and internal features of face. Recognition is more dependent on the external features of the face, such as the outline of the head, than on the internal features. Of course, there are some same affecting factors between unfamiliar faces and familiar face recognition. There is sheltering, inversion and so on. There are different affecting factors. There are view angle, expression, internal and external features. Finally, the paper explores the process in which unfamiliar faces may become familiar faces. What is a main coding form during unfamiliar faces becoming familiar faces?