The invention relates to a heat preservation and moisture retention method for base plate concrete of a large-size tunnel. The heat preservation and moisture retention method comprises the steps of after concrete is poured in a bin, covering the concrete bin surface by geotechnical cloth, and performing water flowing or scattering maintenance on the surface of the geotechnical cloth; after the concrete enters a cooling stage, under a condition of retaining the moisture of the surface, covering the surface of the geotechnical cloth by at least one layer of polyethylene thin film, and covering the polyethylene thin film by at least one polystyrene foam coiled material or at least one heat preservation quilt for maintenance. According to the heat preservation and moisture retention method, the heat preservation and moisture retention effect of the base plate concrete of the large-size tunnel can be enhanced, the quality is easily controlled, the cracking risk is reduced, the crack treatment cost is saved, the safety of the operating period is improved, and interferences on the concrete bin surface and the side surface are avoided; heat preservation and moisture retention are continuous, and the concrete performance is easy to guarantee; the heat preservation and moisture retention method is particularly suitable for temperature control anti-cracking construction of the base plate concrete of the large-size tunnel.