The invention discloses recycled concrete beneficial to improvement of impermeability and a preparation method of the recycled concrete. The recycled concrete is prepared from 50-90 parts of fly ash, 160-240 parts of cement, 25-45 parts of slag powder, 750-1100 parts of modified recycled coarse aggregate, 300-550 parts of natural fine aggregate, 90-120 parts of modified recycled PET (Polyethylene Terephthalate) plastic particles, 5-8 parts of an additive and water, the additive comprises a water reducing agent, an air entraining agent, an early strength agent and a waterproof agent, and the recycled concrete comprises the following components in parts by weight: 75 parts of fly ash, 210 parts of cement, 30 parts of slag powder, 960 parts of modified recycled coarse aggregate, 320 parts of natural fine aggregate, 95 parts of modified recycled PET plastic particles, 0.5 part of the water reducing agent, 1.6 parts of the air entraining agent, 7.5 parts of the early strength agent, 2.3 parts of the waterproof agent and water. According to the recycled concrete beneficial to improvement of impermeability and the preparation method thereof, batch and rapid preparation of the recycled concrete is facilitated, the quality of the recycled concrete is ensured, improvement of the impermeability of the recycled concrete is facilitated, and reutilization of the recycled concrete is ensured.