The invention provides a method for preparing zinc-indium alloy powder by electrochemical co-deposition, and relates to a preparation method of zinc-indium alloy powder. The method for preparing the zinc-indium alloy powder by the electrochemical co-deposition aims at solving the technical problem of non-uniform distribution of indium in a zinc anode of a zinc-silver oxide cell. The method comprises the steps of 1, preparing a deposition solution through ZnSO4, In2(SO4)3, Na2SO4, EDTA and citric acid; 2, building a deposition system by treating a copper sheet as a negative electrode and a high-purity zinc sheet as a positive electrode; 3, depositing under a constant current condition; and 4, drying the powder obtained on the copper sheet in vacuum to obtain the zinc-indium alloy powder. The zinc-indium alloy powder is of a branch structure; indium is uniformly distributed; and the zinc-indium alloy powder can be used for preparing the zinc-silver oxide cell.