The embodiment of the invention discloses a method and a device for constructing a digital core. The method comprises the following steps: performing CT scanning on a first core sample, and determining the CT binarized image of the first core sample based on the obtained CT scanning result; scanning a second core sample by using a scanning electron microscope, and determining the scanning electronmicroscope binarized image of the second core sample based on the obtained electron microscope scanning result; extracting a training image from the scanning electron microscope binarized image; andcomparing the training image with a target CT sub-image in the CT binarized image, correcting the CT binarized image according to the obtained comparison result, and constructing the digital core of atarget area according to the corrected CT binarized image. The method and the device, provided in the embodiment of the invention, can improve the construction precision of the multi-scale porous three-dimensional digital core.