The invention relates to a method for treating cyanide-containing waste water, which comprises: introducing the cyanide-containing waste water into an electrolyzer for electrolysis; decomposing, oxidizing and reducing the cyanides, CN- and NH3-N in waste water and breaking and degrading the cyanides, CN- and NH3-N in waste water into micromolecular or insoluble precipitates; and removing the precipitates by flocculation. Compared with the prior art, the method has the advantages of avoiding adding any other chemical, achieving high degradation effect and the like.