Embodiments for adaptively forming color Doppler images in an ultrasound diagnostic system are disclosed. A method of forming a color Doppler image in an ultrasound diagnostic system comprises: scanning a first set of scan lines set at a full scan region to detect at least one scan line that passes a moving object in the full scan region among the first set of scan lines; setting a second set of scan lines based on the detected scan lines; and scanning the second set of scan lines to form a first color Doppler image.