Disclosed are an X-ray imaging system and method, and the system comprises an X-ray source, a high-voltage generator, a collimator, a digital flat-panel detector, and a host computer; a position relationship between a projection area and a subject is visually displayed through a display screen; as an image frame on the screen is directly dragged to a corresponding position of an image of the subject presented on the screen or an area of interest is drawn, the collimator automatically drives a collimating sheet to move and enables the projection area to move to an observation position required by the subject, and information about the area of interest is transmitted to the detector as an input for selecting a response area of automatic exposure control (AEC). The collimator cooperates with digital automatic exposure control (DAEC), so that a strict requirement is no longer existent for patient positioning.