Method and device for training classifier, method and device for recognizing picture

A method and device for training a picture classifier are provided. The method includes: A, dividing a training picture set for the classifier training into one positive example sample set and more than two negative example sample sets; B, determining a feature group for distinguishing the positive example sample set and the negative example sets with respect to each negative example sample set; C, training and obtaining the classifier through the feature group. Also, a method and device using the picture classifier to recognize the picture are provided.