The invention discloses a treatment method of cadmium ion in acidic non-cyanide cadmium plating wastewater containing no strong coordination agent EDTA. When pH of cadmium plating wastewater is 2.47-9.34, sodium dimethyldithiocarbamate and cadmium ion react to generate cadmium dimethyl dithiocarbamate precipitate; after the precipitate is separated, content of cadmium ion in discharged wastewater meets requirements of GB 21900-2008 ''electroplating pollutant discharge standard'' Table 2. When pH of the wastewater is 4.43-6.73, sodium dimethyldithiocarbamate precipitate cadmium, cadmium ion in the wastewater meets requirements of GB 21900-2008 ''electroplating pollutant discharge standard'' Table 2.