The utility model relates to an improved sludge pulverizer, which comprises a machine body, a main shaft and a cutter bit, wherein the machine body drives the main shaft through a motor, the main shaft extends into a drying room, a layer of interlayer type protective cover with a heat preservation layer is arranged outside the extending section of the main shaft, the front end of the main shaft is provided with a shaft end sealing cover and extends into a groove of the cutter bit, the root part of the main shaft is provided with a cooling air inlet, and the shaft end sealing cover of the main shaft is provided with a cooling air outlet. The utility model has the beneficial effects that the extending end of the main shaft is provided with the interlayer type protective cover with the heat preservation layer, circulating air is used as a cooling medium, the shaft end sealing cover extends into the groove of the cutter bit, and the groove of the cutter bit forms a protective screen to the cooling air outlet, so when cooling air enters from the root part of the main shaft and is sprayed out from the sealing cover at the front end, the sprayed air forms air resistance to prevent splashed particles in the drying room from falling into the protective cover. The improved sludge pulverizer has a heat insulation effect, abrasion is avoided, the durable performance of a bearing and the working stability of the whole pulverizer are effectively improved, and the service life of the pulverizer is prolonged.