1. A face detector training method, comprising: performing a training process by: collecting face and non-face images as a training image sample set; extracting a flexible block based local binary pattern (FBLBP) feature of the face and non-face images to form an FBLBP feature set; and using the FBLBP feature and a GentleBoost algorithm to perform training, to obtain a first classifier, wherein the first classifier comprises several optimal second classifiers, and each optimal second classifier is obtained by training by using the GentleBoost algorithm; repeating the training process to obtain multiple layers of first classifiers; and cascading the multiple layers of first classifiers to form a face detector.