The present invention provides a magnetic resonance imaging system for imaging a subject by a multi-shot imaging. The magnetic resonance imaging system comprises an acquiring unit for acquiring MR raw data corresponding to a plurality of shots; an imaging unit for generating a plurality of folded images from the MR raw data, wherein each of the plurality of folded images is generated from a subset of the MR raw data; a deriving unit for deriving magnitude of each pixel of each folded image; a detecting unit for detecting a motion of the subject during the multi-shot imaging based on similarity measurements of any two folded images of the plurality of folded images, wherein the detecting unit further comprises a first deriving unit configured to derive the measured similarities; and a reconstructing unit for reconstructing a MR image of the subject based on MR raw data obtained according to a detection result of the detecting unit. Since the partially acquired MR raw data is used for motion detection directly, it would be more rapid and stable.