The invention provides a sludge dewatering and drying system, relating to the field of sludge treatment equipment. The sludge dewatering and drying system comprises a cyclone separator and a sludge centrifugal dewaterer, wherein the sludge centrifugal dewaterer comprises a casing prepared from a thermal-insulation material; the casing is provided with a hot air inlet pipe, a liquid-phase outlet and a solid-phase outlet; the hot air inlet pipe is connected with a high-temperature hot air source; a rotating drum is arranged in the casing; a gap is left between the rotating drum and the casing; a spiral pusher is installed in the rotating drum; and a feed port of the cyclone separator is connected with the solid-phase outlet of the sludge centrifugal dewaterer in a sealing mode. The casing of the sludge centrifugal dewaterer is prepared from the thermal-insulation material to reduce the heat loss, so that a higher temperature is kept in the sludge centrifugal dewaterer, thereby enhancing the drying effect.