According to the principles of simultaneous chemical equilibrium and electronic charge neutrality, the thermodynamics of Au-NH 4 Cl-NH 3 -H 2 O system was studied by using the exponential computation method and through MATLAB programming, and the solid figure of potential-c(NH 4 Cl)-c(NH 4 OH) was drawn. The results show that when the sum concentration of Au + and Au 3+ is equal to 5 × 10 −5 mol/L, φ(Au + /Au) is about −0.2 V; when the sum comes up to 0.5 mol/L, the value of φ(Au + /Au 3+ ) increases to 0.2 V. In this case, φ(O 2 /OH − ) is as high as 0.7 V. This means that it is feasible to extract gold in this system. In addition, to predict the feasibility of reducing gold from the Au(I)-NH 4 Cl-NH 3 -H 2 O system with copper or zinc powder, the solid figures of potential-c(NH 4 Cl)-c(NH 4 OH) for both systems of Cu-NH 4 Cl-NH 3 -H 2 O and Zn-NH 4 Cl-NH 3 -H 2 O were also drawn. The results indicate that both copper and zinc powders can reduce Au + into metal gold, and zinc powder can also reduce H 2 O into H 2 , while copper powder can not. The leaching results of a cuprous gold ore show that the extraction of gold can reach 80% in this system. The preliminary results of reduction with copper and zinc powders show that with deoxygenizing, the reduction effects are relatively good.