Objective To synthesize a novel aurous compound and to analyze the feasibility of its application in cyanide-free gold plating. Methods Chloroauric acid was used as the gold liquid and cysteine as the ligand. Aurous compound (NaAu(Cys)2) was synthesized under the alkalescent environment, and related physical and chemical properties were studied by elemental analy- zer, infrared spectroscopy, UV-Vis spectrometer, thermogravimetric analyzer and conductivity meter. Results The results indicated that the molecular formula of the product was NaAu(Cys) 2 . IR spectra revealed a strong coordinating bond formed between Au(I) and the aurous in cysteine. UV-Vis revealed its characteristic adsorption was in the range of 205 ~ 210 nm. The DTA curve ex- plained the product was thermally stable before the temperature reached 170 ℃ . Conductivity data showed the complex was a typi- cal ionic compound. By means of single factor and orthogonal tests the optimized electroless nickel / immersion gold indexes were obtained: operating temperature = 45 ℃ , pH = 2, aurous concentration = 2 g / L, respectively. Quality inspection under these condi- tions showed the deposited gold particles were in excellent bonding with controllable plating rate and good gold-plating effect. Con- clusion A novel aurous compound was synthesized with stable physical and chemical properties,which is expected to be used in the cyanide-free gold plating industry.