The invention discloses a copper-based low-temperature conversion catalyst which is mainly prepared from copper oxide, zinc oxide, aluminum oxide, an auxiliary I, an auxiliary II and an auxiliary III. The invention further discloses a preparation method of the catalyst. The method includes the steps that copper nitrate, zinc nitrate, aluminum nitrate and a soluble salt solution of the auxiliary III are dissolved in water; the obtained salt solution is added into a precipitator solution at 50-90 DEG C under the continuous stirring condition for co-precipitation; the auxiliary II is added into precipitate to be stirred and mixed, the mixture is filtered, washed and dried after mixing, and a catalyst precursor is obtained; the catalyst precursor is dipped in a salt solution containing the auxiliary I in advance, graphite is added to be evenly mixed after drying and roasting, and the copper-based low-temperature conversion catalyst is obtained through tabletting. According to the copper-based low-temperature conversion catalyst, the specific surface area is 50-120 m<2>/g, the methyl alcohol generation amount is low, activity is high, heat resistance is good, high strength can still be kept after the catalyst is subjected to reduction and used for a long time, and the catalyst is particularly suitable for low-steam-gas-ratio operation conditions of an energy-saving ammonia factory.