Chloroauric acid was prepared by ion-exchange membrane electrolysis with gold as anode, graphite as cathode, saturated calomel electrode as reference electrode and hydrochloric acid solution as electrolyte. The anodic behavior of gold in the preparation process and the effects of experimental conditions such as chloride ion concentration, pH and hydrogen peroxide content on the preparation process were explored, and the reaction mechanism was analyzed and explored. The results show that the chemical formula of the sample obtained in the experiment is HAuCl4 ? 4H2O. There is basically no loss of gold in the process of the experiment, and the yield can reach more than 94%; Electrochemical tests showed that the electrolysis of gold to au3+ occurred between 0.8-1.3v, and the passivation voltage was 1.3V; Under the condition of pH 1.0, the best preparation conditions are electrolytic voltage 1.25V, hydrogen peroxide dosage 5mmol,; In the process of electrolysis, reducing the pH of electrolyte and increasing the concentration of chloride ion in electrolyte can promote the electrolysis of gold. In addition, the peak potential decreases with the decrease of pH; Nyquist diagram shows that the preparation process is controlled by charge transfer and diffusion mixing. With the increase of cl- concentration in the solution and the addition of hydrogen peroxide, the influence of diffusion control weakens, and the transition from mixing control to charge transfer control. Compared with the traditional process, the preparation of chloroauric acid by diaphragm electrolysis has the advantages of no pollution, easy operation, high safety and small hydrochloric acid loss.