The dehydrated sludge with moisture content of 75% to 83% is dehydrated at normal temperature and pressure with the addition of curing agents, heavy metal inhibitors, cementing agent, etc. The dehydrated sludge then forms solidified bulks which completely meet the requirements for landfill after 36 hours of treatment. The solidified sludge basically maintains its strength and tightness after being dipped in rainwater for a long time. Through chemical reaction, by which heavy metals are absorbed into the chemical structures of the compounds formed during the reaction with the curing agents, and physical reaction, i.e. the cure of the products formed during the reaction, heavy metals in the sludge will be wraped.