The invention discloses an environment-friendly energy-saving high-conversion-ratio rare-earth catalyst and a preparation method thereof. The environment-friendly energy-saving high-conversion-ratio rare-earth catalyst is prepared from the following raw materials in percentage by mass: 0.01-10% of a lanthanum-containing compound, 0.01-10% of a cerium-containing compound, 0.01-10% of a neodymium-containing compound, 0.01-10% of a praseodymium-containing compound, 3-15% of V2O5, 1-3% of thiosulfate, 1-15% of a caesium-containing compound, 1-5% of a surfactant, 1-5% of an organic high-molecular compound, 1-30% of hydroxide, 5-30% of diluted sulphuric acid, 0.1-10% of anhydrous sodium sulphate, 0.1-7% of phosphoric acid, 1-15% of sulfur and the balance of diatomite. The material components cooperatively act, so that the stability of the catalyst is improved, and the service life of the catalyst is remarkably prolonged, and an ignition temperature is remarkably reduced.