An ultrasound imaging breast tumor detection and diagnostic system and method is disclosed. The method uses the system to acquire a plurality of 3D breast ultrasound images, and then to cut out multiple regions from the 3D breast ultrasound images using a 3D means shift algorithm, and then to acquire the mean grayscale value (MGV) of each region, and then to classify the regions to groups subject to the mean grayscale value (MGV), and to merge each of the regions of the darkest group with adjacent regions of the similar grayscale into a respective suspicious tumor tissue full region, and then to recognize each suspicious tumor tissue full region to be a tumor tissue region or non-tumor tissue region. Thus, using region as the basic computing unit, tumor tissues are quickly recognized from the 3D breast ultrasound images.
