The invention discloses a breast ultrasound image self-learning extraction method and system based on a stacked noise reduction self-encoder. The method comprises the steps of extracting manual shallow layer features from each ultrasound breast lesion area image ROI as a training sample to form a training sample set set_unlabeled = {x(1), x(2), ..., x(n)}, the i-th sample x(i) belonging to [0, 1]<d>, i = 1, 2, ..., n; based on the training sample set, training a first noise reduction self-encoder DAE1; after training the first noise reduction self-encoder, re-entering the training sample set, using the self-encoder trained in the step S4 to extract feature expressions obtained through hidden layer learning of all the samples to form a new sample {y(1), y(2), ..., y(n)}, and using the new sample as an input of a second noise reduction self-encoder DAE2 to train the second noise reduction self-encoder. The invention achieves extraction of breast ultrasound image features, thereby provides valuable reference opinions for clinic diagnosis, and improves the accuracy and efficiency of breast cancer diagnosis.