An ultrasound system, comprising: an ultrasound data acquisition unit including an ultrasound probe for transmitting ultrasound signals to a target object and receiving ultrasound echo signals reflected from the target object, the ultrasound data acquisition unit being configured to acquire ultrasound data based on the ultrasound echo signals, the ultrasound data acquisition unit being further configured to detect an orientation and a scanning direction of the ultrasound probe; and a processor configured to form a volume data based on the ultrasound data, a three-dimensional ultrasound image using the volume data, and an orientation help, OH, view showing a spatial orientation of the volume data on a display region, the OH view including the three-dimensional ultrasound image, a probe orientation marker indicating the detected orientation of the ultrasound probe, and a scanning direction marker indicating the detected scanning direction, wherein the three-dimensional ultrasound image is overlapped with the OH view, characterized by comprising: a user interface for receiving a first user instruction for setting a geometrical operation including rotation, reduction, enlargement and movement of the OH view, wherein the processor is further configured to set the geometrical operation of the OH view in response to the first user instruction, to provide a clip plane indicating an image of a selected one of reference planes on the OH view, and wherein the OH view further includes the clip plane and a region of interest. an ultrasound data acquisition unit including an ultrasound probe for transmitting ultrasound signals to a target object and receiving ultrasound echo signals reflected from the target object, the ultrasound data acquisition unit being configured to acquire ultrasound data based on the ultrasound echo signals, the ultrasound data acquisition unit being further configured to detect an orientation and a scanning direction of the ultrasound probe; and a processor configured to form a volume data based on the ultrasound data, a three-dimensional ultrasound image using the volume data, and an orientation help, OH, view showing a spatial orientation of the volume data on a display region, the OH view including the three-dimensional ultrasound image, a probe orientation marker indicating the detected orientation of the ultrasound probe, and a scanning direction marker indicating the detected scanning direction, wherein the three-dimensional ultrasound image is overlapped with the OH view, characterized by comprising: a user interface for receiving a first user instruction for setting a geometrical operation including rotation, reduction, enlargement and movement of the OH view, wherein the processor is further configured to set the geometrical operation of the OH view in response to the first user instruction, to provide a clip plane indicating an image of a selected one of reference planes on the OH view, and wherein the OH view further includes the clip plane and a region of interest. a user interface for receiving a first user instruction for setting a geometrical operation including rotation, reduction, enlargement and movement of the OH view, wherein the processor is further configured to set the geometrical operation of the OH view in response to the first user instruction, to provide a clip plane indicating an image of a selected one of reference planes on the OH view, and wherein the OH view further includes the clip plane and a region of interest.