There are provided an ultrasound imaging system and a method of forming a plurality of scan lines and frames by using receiving signals provided by transducers in a probe. Main scan lines, which are selected among the scan lines and supplement scan lines determined with the others, are assigned to each scan line data forming unit in the ultrasound imaging system. A partial data of the main scan line and a first supplement data of the supplement scan line are formed with receive data obtained from receive signals from at least one transducer. A second supplement data provided from other scan line data forming units is applied to the partial data of the main scan line to form a scan line data of the main scan line.