A fast and accurate method of automatic detection and location of the mouth is proposed according to the feature extraction of face identification. At first, mouth region is roughly detected by Adaboost in face image, so the range of search is reduced. Then, mouth contour is detected by local gradient operator and binarized by Ostu threshold method. Finally, the mouth corners are accurately localized by Chain code tracking. The experiment results indicate that this method can detect and locate mouth corners fast and exactly. It can reduce the influence of facial expression and posture and improve the recognition rate of face identification.