The invention discloses a sludge reduction combined treatment system which comprises a sludge storage tank, a dehydration-pressure filtration device, a middle sludge storage bin, a sludge forming machine and a belt-type drier, wherein the dehydration-pressure filtration device comprises a piston cylinder and a piston capable of rotary reciprocation; a flexible filter carrier is arranged in the piston cylinder, and is connected with the piston and pulled by the piston; a guide groove is arranged inside the filter carrier; the belt-type drier is provided with a drying zone and a cooling zone; the drying zone is connected with a drying fan and an air heater through a pipeline, and connected into the drying zone to form a dry air loop; and the cooling zone is connected with a cooling fan and a granule cooler through a pipeline, and connected into the cooling zone to form a cooling air loop. Under the combined actions of the piston and filter carrier, the integral sludge is sufficiently filtered, the water content of the sludge is lowered to 70% or below, and an economical low-temperature belt-type drying technique is adopted to greatly lower the heat loss cost of drying.