To provide a turbidity prevention construction method for precipitating dredging sludge to the bottom of the sea without generating any turbidity in the sea area in the case of dropping the dredging sludge under the sea by using a waste gypsum board burned product and paper ash.

The turbidity prevention construction method for dropping dredging soil under the sea includes: inputting 0.05 to 10 wt.% of hemihydrate gypsum and 0.2 to 0.5 wt.% of inorganic high polymer to the dredging soil with respect to the soil weight 100 wt.% of the dredging soil of 100 to 200% of an initial water content, or inputting 0.05 to 10 wt.% of paper sludge ash and 0.2 to 0.5 wt.% of inorganic high polymer to the dredging soil, or inputting the total of 0.05 to 10 wt.% of hemihydrate gypsum and paper sludge ash and 0.2 to 0.5 wt.% of inorganic high polymer to the dredging soil; and stirring and laying and then dropping the dredging soil under the sea. Thus, it is possible to solve the problem by a turbidity prevention construction method using a waste gypsum board burned product and paper ash.