The invention discloses a high-permeability concrete sealed waterproofing agent and a preparation method thereof. Most of permeable waterproofing agents on the market presently have the problems of too high surface tension, high viscosity, insufficient permeation depth, bad sealing effect for microcracks in concrete, and unobvious improvement for the waterproofing and anti-permeation performance of concrete. The waterproofing agent disclosed by the invention comprises 500-900 parts of lithium silicate solution, 5-50 parts of modifier, 1-20 parts of retarder, 0-50 parts of reinforcing agent, 5-50 parts of permeating agent and 0-200 parts of deionized water, wherein the lithium silicate solution is a colourless and transparent aqueous solution with a modulus of 4-5 and a solid content of 20-30%; and the permeating agent is one or more of polyether-modified organosilicone and fluorocarbon surfactant. According to the waterproofing agent disclosed by the invention, the lithium silicate solution is modified through the modifier, and the high-efficiency permeating agent and retarder are adopted, thus the surface tension of the waterproofing agent is greatly reduced, and the permeation depth is increased.