The invention provides a three-dimensional-digital-model generation method used for constructing a rock core model. The three-dimensional-digital-model generation method used for constructing the rockcore model includes: step 1, acquiring original material used for constructing a three-dimensional digital model of the rock core model; step 2, binarizing an image obtained in the step 1; step 3, finding pore points for the image after processing of the step 2, filtering out micropores, and carrying out communication on the pores; step 4, normalizing the image after processing of the step 3; step 5, carrying out size expansion on the image after processing of the step 4; and step 6, carrying out stereoscopic processing on the image after processing of the step 5. According to the three-dimensional-digital-model generation method used for constructing the rock core model, the suitable-size model can be made according to research needs and performance of a 3D printer, any number of rock core models with the same fracture structure can be made according to needs, transparent printing material is used, and the made model has observability.