The present invention discloses a method for extracting AIF and an application thereof to DCE-MRI. The method comprises steps: contacting a target tissue with a contrast agent to obtain a plurality of images using the plurality of images to work out the tissue concentration curve of the contrast agent in each voxel calculating the purity of the tissue concentration curve of each voxel according to the tissue concentration curves and extracting the voxel having the highest purity as the optimized arterial location and extracting the tissue concentration curve of the voxel having the highest purity as the arterial input function. The extracted AIF is applied to a pharmacokinetic model to obtain associated pharmacokinetic parameters. The present invention not only improves the accuracy and reliability of the derived quantitative indexes but also promotes the efficiency of the quantitative analysis.