The invention discloses a landfilled civil sludge curing agent and a deep dehydrating method thereof and belongs to the field of civil sludge treatment. For landfilling the civil sludge, on one hand, a curing agent in a certain proportion is added before landfilling, so that the secondary deep dehydrating treatment difficulty is increased; on the other hand, a complicated biochemical reaction is performed on the landfilled sludge in an anaerobic environment, so that the moisture content is increased, and the sludge components become more complicated. For the characteristics of the landfilled civil sludge, the used curing agent contains carbide slag, sulfate aluminum cement, mineral powder, coal ash and an iron salt which are added by a certain sludge dry base percentage according to an adding sequence and stirring time to condition the sludge, and the dehydrating performance of the sludge is effectively improved, so that the colloidal particles in the sludge are destabilized and flocculated, a lot of water is removed, a basic condition for deep dehydration of the sludge is created, and the water content of a mud cake after dehydration can be reduced to 50-60%. The landfilled civil sludge curing agent disclosed by the invention solves the problem of deep dehydrating of the landfilled civil sludge, and the dehydrated sludge can be used as a resource. The curing agent is easy to obtain and low in cost.