Disclosed is a clean method for preparing layered double hydroxides (LDHs), in which hydroxides of different metals are used as starting materials for production of LDHs by atom-economical reactions. The atom efficiency of the reaction is 100% in each case because all the atoms of the reactants are converted into the target product since only M2+(OH)2, M3+(OH)3, and CO2 or HnAn− are used, without any NaOH or other materials. Since there is no by-product, filtration or washing process is unnecessary. The consequent reduction in water consumption is also beneficial to the environment.