The invention provides a preparation method of a monoatomic catalyst by taking mesoporous titania as a carrier. The preparation method comprises the following steps: dissolving polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) into an ethanol solution, after dissolution is ended, respectively adding a certain amount of concentrated sulfuric acid and concentrated hydrochloric acid, stirring at room temperature for a certain time, then adding isopropyl titanate, stirring for a certain time, then adding chloropalladic acid, and preparing a precursor of Pd@TiO2 bySolvent volatilization induced self-assembly technique; drying the precursor, then putting into a muffle furnace, heating to a certain temperature in a program heating way, and keeping the temperature for a period of time; after roasting is ended, reducing at a certain temperature by using an H2/N2 gas mixture, thus obtaining a palladium monoatomic catalyst with uniform particles. The monoatomiccatalyst prepared by the preparation method has the advantages that the process is simple, metal atoms are dispersed uniformly on the carrier, the repeatability is good, the range of suitable acids iswide, a product is a nanoparticle in a hexagonal prism or sphere shape, therefore the pore size distribution is uniform, the catalytic performance is excellent, and mass production can be realized.