The invention discloses a biological formaldehyde remover and a preparation method thereof. The biological formaldehyde remover is prepared by extracting leaves or/and twigs or/and barks of sweet clover, leaves or/and twigs or/and barks of cinnamomum camphora, camellia seed cakes and coarse tea leaves with water, wherein the mass ratio of the components is 3:2:3:2. The biological formaldehyde remover disclosed by the invention is a biological reagent which is environment-friendly, when the biological formaldehyde remover is uniformly added into a chemical containing formaldehyde, formaldehyde can be effectively adsorbed and degraded, damage caused by the chemical containing formaldehyde to health of human bodies can be reduced, and the biological formaldehyde remover can be effectively used in plywood machining and building decoration coatings.