The invention discloses an oil-soluble formaldehyde scavenger and belongs to the technical field of indoor air scavengers. The scavenger specifically comprises a spherical carrier and a dicyandiamidepowder reactant adhering to the spherical carrier, wherein the spherical carrier is subjected to surface modification with N-octadecyl biquaternary ammonium salt. The spherical carrier formed throughmodification with N-octadecyl biquaternary ammonium salt adopts a hydrophobic structure on the surface and can penetrate through an artificial board to adhere to the surface of the board; gaseous formaldehyde around the board can be gathered to the periphery of the spherical carrier under the trapping action of N-octadecyl biquaternary ammonium salt, so that the formaldehyde can make contact and react with dicyandiamide, after water molecules of a product are absorbed, dicyandiamide resin gradually settles on the surface of the spherical carrier and adsorbed by the spherical carrier, and the scavenger has high formaldehyde scavenging efficiency and lasting effects under the synergistic effect of the three factors.