The invention relates to a treatment method of dehydrated sludge in a domestic sewage treatment plant. The treatment method comprises the following steps: evenly mixing limestone, magnesia and bauxite which are weighed in a ratio of (40%-60%):(20%-30%):(20%-30%) by weight percent and then firing for 1-2 hours at the temperature of 900 DEG C-1200 DEG C so as to obtain a sludge solidifying agent; adding the sludge solidifying agent in the dehydrated sludge in the ratio of dehydrated sludge to sludge solidifying agent of (90%-95%):(5%-10%) by weight percent, and then stirring; after evenly mixing, paving the mixture obtained in the former step to the thickness of 20-30 cm in the open air, and placing for 48 hours so as to obtain a sludge solidifying body; and finally, performing landfill treatment. According to the invention, the solidifying time is short, and the adding amount of the sludge solidifying agent is less; by using the treatment method, sludge can be modified, and the stabilization of sludge is promoted; the bulking of the sludge solidifying body is small, the stability and mechanical strength of the sludge solidifying body are high, and secondary pollution can not be caused; and the solidifying technological process is simple and convenient for operation, and the investment and treatment costs are low, thus the treatment method in the invention can be widely applied to stabilization, reduction and innocent treatments of dehydrated sludge in a sewage plant.