At present, the preparation method of the n-type GaAs ohmic contact electrode is mainly based on the evaporation method. However, this method has the disadvantages of high equipment price and waste of electrode materials. Ohmic contact electrode AuGeNi/Au of n-type GaAs was prepared by ion sputtering. By optimizing the preparation process, the electrode layer with smooth surface, uniform composition and no segregation can be obtained. After annealing at 400 ℃ in argon atmosphere, the Schottky contact between the electrode and GaAs changes to ohmic contact, and the resistance between two electrodes decreases to 1/20 of the original. Choosing the appropriate annealing temperature (400 ℃ to 500 ℃), a small contact resistivity (10-6 Ω·cm2) can be obtained, which can improve the stability of the device and reduce energy consumption. The contact resistivity is higher when the annealing temperature is lower than 400 ℃ or higher than 500 ℃, which is related to the fact that the ohmic contact has not yet formed and the “spheroidization” of Au-Ge alloy, respectively. The preparation method and process have the advantages of low equipment cost, simple process, saving electrode materials, good economic benefits and practical value, and are suitable for scientific research laboratories.