A modified procedure for electroplating wastewater treatment using formaldehyde and hydrogen peroxide can destroy free cyanide. The representative diagram which is quite sensitive on reaction temperature is showed for this kinds of treatment. Principally free cyanide and some kinds of cyanide complex should be treated first, and then toxic heavy metals can be removed because cyanide component will be inhibited to remove other pollutants, if it is not destroyed perfectly. Formaldehyde and hydrogen peroxide are added in controlled amounts to cyanide treatment tank. Reasonable amounts of these chemicals are (HCHO/CN)=0.9 and ($H_2O_2/CN$)=1.1 in molar ratios, it is also variable on reaction temperature. Of course, actual treatment processes depending on plating material and chemical are good applicable, also to systematize operation manual for treating electroplating wastewater process, further works are desirable.