The invention discloses an artificial board formaldehyde adsorbing and fixing agent, which comprises a component A and a component B, wherein the component A comprises 90-95 parts of diatomite with 200 meshes, 2-4 parts of a silane coupling agent and 3-8 parts of urea; the component B comprises 40-60 parts of phosphate buffered saline, 35-55 parts of solid ammonium sulfate and 2-5 parts of liquid paraffin; the component A and the component B are respectively and independently stored and cannot be mixed; the component A is directly added to an adhesive during artificial board production and takes 4-5% of the weight of the adhesive; the component B is directly sprayed on the surface of an artificial board, and the spraying amount is 40-50 g/m<2>. The invention further provides a preparation method of the artificial board formaldehyde adsorbing and fixing agent. The artificial board formaldehyde adsorbing and fixing agent can highly effectively adsorb and fix artificial board formaldehyde, and effectively reduces the free formaldehyde emission, so that the environment protection level of the board is up to E0.