The invention discloses ITO-Ag-ITO etching liquid for an AM-OLED display screen and a preparation method. The etching liquid is prepared from phosphoric acid, acetic acid, nitric acid, additives, surfactants and pure water. The preparation method of the etching liquid comprises the steps that the rotating speed of a stirrer of a dosing tank is kept at normal temperature and pressure, the pure water, the phosphoric acid, the acetic acid, the nitric acid, the additives, the surfactants and the balance pure water are sequentially added into the dosing tank, and after full stirring is conducted, the ITO-Ag-ITO etching liquid is prepared by introducing a fully-stirred mixture into a filter for filtration. According to the ITO-Ag-ITO etching liquid for the AM-OLED display screen and the preparation method, the ITO-Ag-ITO etching liquid is small in particle size and high in purity, the etching rate to different metal is basically the same, and reaction is stable; the etching rate can be controlled by adjusting the concentrations of the phosphoric acid and the nitric acid, the surface of a substrate etched through the etching liquid is clean and tidy, residues do not exist, the intermetallic layering phenomenon does not exist, remaining lines are flat and smooth, and the etching angle is kept between 70 degrees to 90 degrees.