Abstract: Eyewitness identification plays an important role in court judge. DNA evidence shows that identification maybe not reliable. Psychologists try to understand variables influence the accuracy of identification. This article introduces the development of eyewitness identification in the west, analyzes estimator variables and system variables that influence the performance of eyewitness identification, and then discusses the problems of theory relevant and external validity

Key words: eyewitness identification, estimator variable, system variable, base rate