The invention discloses recycled concrete capable of reducing porosity and a preparation method of the recycled concrete. The preparation method comprises the following steps: step 1, carrying out pretreatment such as collection, cleaning, beating and impurity removal on waste concrete; 2, the pretreated concrete blocks are subjected to crushing, screening and grading treatment; step 3, mixing the treated concrete particles with raw materials in a corresponding proportion to form concrete recycled aggregate; and 4, treating the recycled aggregate to form mortar, and pouring and vibrating to form new recycled concrete. According to the recycled concrete capable of reducing the porosity and the preparation method, gaps among slurry can be filled by adding the water reducing agent, the nano silicon dioxide, the reinforcing filler and the acid solution, so that the porosity is reduced, and meanwhile, the swelling agent, the Portland cement, the mineral powder, the anti-cracking agent, the reinforcing filler and the curing filler are added, so that the porosity is reduced. The performances of deformation resistance, impact resistance, compression resistance, permeation resistance and the like of the concrete can be enhanced.