There is provided an ultrasound imaging system, which includes: an ultrasound diagnostic unit for providing 3D volume data of an object and its neighboring region, wherein the 3D volume data is formed with a number of frames; a pre-processing unit for selecting a predetermined number of key frames from the frames; a segmentation unit for segmenting each of the key frames into object regions and non-object regions; a texture-based region classifying and merging unit for classifying the object and the non-object regions into object and non-object sub-regions based on the texture thereof, and removing the non-object sub-regions and merging the object sub-regions; a surface determining unit for extracting contours of the object in the key frames and determining a 3D surface of the object by connecting the contours; and a rendering unit for forming masked volume with the 3D surface and forming a 3D ultrasound image of the object by rendering the masked volume.