Disclosed are a gadolinium complex formed by coordination of gadolinium to the diethylenetriaminepentaacetic acid dianhydride (DTPA) moiety of a pullulan-DTPA conjugate formed by an ester bond between pullulan and DTPA, a preparation method thereof, an MRI contrast composition comprising the complex, and a method of providing information for diagnosis of disease using the complex as an MRI contrast agent. The pullulan-DTPA-Gd complex has a long in vivo half-life, low toxicity, and high MRI signal intensity resulting in clear MRI images, compared to prior gadolinium complexes, indicating that it is advantageously used as an MRI contrast agent. In addition, it is possible to obtain MRI images allowing one to differentiate between diseased liver tissue and normal liver tissue, indicating that it is used as an MRI contrast agent for the liver.