The invention provides a preparation method of light-weight and high-strength concrete containing nano-silica. According to the preparation method, components are weighed in proportion, and the mass ratio of cement to water to floating beads to shale ceramisite to stone to medium sand to nano-silica to a water reducer is 1:(0.36-0.40):(0.1-0.15):(1.8-2.2):(0.6-0.8):(1.3-1.5):(0.02-0.03):(0.005-0.01), and then shale ceramisite is soaked in water for 24 h, taken out and dried; the shale ceramisite, the cement, the medium sand and the floating beads are mixed and put into a stirring machine to be stirred, and a mixture is obtained; then nano-silica, water and the water reducer are stirred at a high speed, and a suspension is obtained; finally, the suspension is added to the mixture and stirred, and the light-weight and high-strength concrete containing nano-silica is obtained. The strength of the concrete is improved, the density of the concrete is reduced, micro-cracks and micropores in the concrete are avoided, the compression resistance of the concrete is improved, the price is low, and the practicability is high.