An ultrasound system and a method for forming an ultrasound image are provided to display movement change of an object as an image without the degradation of a frame rate. An ultrasound system includes a transceiver(130), a storage(140), an image processor(150), and an interface unit(110). The transceiver forms a plurality of receiving signals by transmitting and receiving a first ultrasound signal for obtaining a 2D image along a plurality of scan lines. The storage stores a plurality of reception signals. The image processor forms 2D image by reading the plurality of reception signals in the storage. The interface unit receives the first setting information of a first interest region for obtaining a color flow image and the second setting information of a second interest region for obtaining a color spectrum image.본 발명은 대상체로부터 반사되는 초음파 신호의 반사 계수를 영상으로 나타내는 2D 모드(2D mode) 및 2D-모드 영상에 설정된 컬러박스(color box)에 해당하는 영역의 혈류 속도를 컬러 플로우 영상(color flow image)으로 나타내는 컬러 도플러 모드(color doppler mode)와 함께 혈류의 시계열적인 변화를 컬러 스펙트럼 영상으로 나타내는 컬러 스펙트럼 모드를 동시에 제공한다.
