The invention discloses a tanning agent for leather synthesis. The tanning agent comprises, by mass, 250 parts of naphthol, 229 parts of formaldehyde, 206 parts of sulfuric acid, 5 parts of ammonium persulfate, 59 parts of glacial acetic acid, 156 parts of phenol, 0.01 part of naphthalene, 0.01 part of sodium sulfate, 1 part of crylic acid, and a proper amount of water. The invention further discloses a production method of the leather synthetic tanning agent. The leather synthetic tanning agent is formed by using the naphthol, the formaldehyde, the sulfuric acid, the glacial acetic acid, the phenol, the naphthalene and the like as raw materials. Due to the fact that the components are conventional materials, the cost is low, the leather synthetic tanning agent is conveniently popularized, the leather synthetic tanning agent has the advantages that the tanning capacity and tanning speed are high, and leather obtained after tanning is soft and good in bending performance, and the leather synthetic tanning agent has the certain light resistant performance, the bleaching performance and the packability.