An ultrasound system includes an ultrasound data acquisition unit and a processing unit. The ultrasound data acquisition unit transmits and receives ultrasound signals to and from a target object based on a plurality of steering angles to output a plurality of ultrasound data for obtaining a plurality of ultrasound images corresponding to the steering angles. The processing unit forms the ultrasound images based on the ultrasound data, decomposes each of the ultrasound images into a low pass image having a low frequency component and a high pass image having a high frequency component, performs a blending process of removing a seam artifact upon the low and high pass images for each of the ultrasound images, forms a plurality of restoration images by composing the blended low and high pass images, and forms an ultrasound spatial compound image based on the restoration images.