The invention relates to a paramagnetic metal complex modified by an aspartic acid-leucine copolymer as well as a preparation method and an application of the paramagnetic metal complex, and is used for solving the technical problems of low biodegradability, low liver targeting property, immunity defects and the like of the existing liver-type macromolecular contrast agent. The paramagnetic metal complex is formed by taking the aspartic acid-leucine copolymer as a carrier, wherein annular 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid ligands are connected on side chains of the carrier. A magnetic resonance imaging contrast agent prepared from the paramagnetic metal complex provided by the invention has the characteristics of a corresponding polyamine multi-carboxy complex, so that the magnetic resonance imaging contrast agent is good in stability, water solubility and relaxation rate, and simultaneously has the targeting property to the liver so as to realize the targeted imaging to improve the imaging contrast ratio and the imaging definition. Thus, the magnetic resonance imaging contrast agent has a good effect for improving the early-stage diagnosis level of diseases of the liver organs.