The invention discloses a thiosulfate silvering additive, a preparation method thereof and electroplate liquid containing the same. The thiosulfate silvering additive comprises 12-18 g / L of lauryl sodium sulfate, 3-5 g / L of polyethylene glycol, 10-13 g / L of nitrogen mustard, 5-10 g / L of cumin, 250-350 g / L of 1,10-phenanthroline monohydrate, 50-100 g / L of dimercaprol dimercaptopropanol, 50-100 g / Lof mercaptoethylamine, 100-150 g / L of ethylene glycol tetraacetic acid (EGTA) and the balance water. The additive provided by the invention enables the dispersity, the stability and the electroplatingperformance of the electroplate liquid to be quite remarkably improved, the pH value does not need to be adjusted repeatedly in the electroplating process, meanwhile, the performance including the smoothness, the adhesive force, the glossiness, the anti-tarish performance and the like of a silvering coating are remarkably improved, the thickness of the coating is further reduced, and phenomena such as fracturing do not exist; and the electroplate liquid provided by the invention does not contain cyanide, the mirror surface of the coating is bright, small in brittleness, good in adhesive force, flat in surface, bright, good in anti-tarish performance and high in heat resistance, application to the multiple fields of decorative electroplating, functional electroplating and the like can be achieved, preplating is not needed, and the bonding force can also be guaranteed.