The invention discloses metal ion supplementing composite alloy powder. The composite alloy powder comprises: alloy AxBy powder particles and a protective layer M covering the surfaces of the alloy AxBy powder particles, wherein A is one of Li, Na, Mg and K; B is one or more of Mg, Ca, Al, Ge, Sn, Sb, Zn, Si, Si / C, SiOz and SiOz / C materials; wherein AxBy is an alloy, an intermetallic compound or asolid solution of A and B, and the protective layer M is a single-layer protective layer or a double-layer protective layer composed of one or more of a metal simple substance, a metal oxide, carbon,carbonate of A, silicate of A or carbonate containing metal elements in B. The metal ions compensated by the alloy powder can meet the requirements of the battery on the active metal ions, so that the performance of the battery is obviously improved.