The invention discloses light aggregate concrete and a preparation method thereof, and relates to the technical field of concrete. The light aggregate concrete comprises the following components in parts by weight: 160-170 parts of cement, 250-300 parts of light aggregate, 10-20 parts of a reinforcing agent, 5-10 parts of a polycarboxylic acid water reducer, 1-5 parts of a dispersant, 5-8 parts ofa retarder, 90-100 parts of coal ash, 190-200 parts of water, 5-10 parts of an inorganic viscosity modifier, and 2-5 parts of cellulose ether. The light aggregate concrete has the advantages of goodworkability and uniformity, suitability for high and remote pumping, and high strength and toughness. In addition, the concrete prepared by the preparation method has the good workability and uniformity, and has the better strength and toughness.