The invention belongs to the technical field of sludge treatment, and particularly relates to a dehydration treatment method for reducing the water content of sludge. The method comprises the two procedures of mixing and granulating the sludge, a dry material, straws and a composite strain BYM, and performing stacking fermentation. According to a principle for the dehydration method for reducing the water content of the sludge in a microbial fermentation way, a great amount of heat can be produced in a microbial fermentation process, and can be used for reducing the water content of the sludge with low cost. Compared with the prior art, the method has the advantages of low energy consumption, low material consumption and low cost; the water content of the fermented sludge is reduced to be lower than 30 percent, the sludge has great development potential, and can be used as an organic compound fertilizer or a building material, and the resource utilization of a product is facilitated.