The invention discloses a method and device for preparing ceramsite from sludge pyrolytic biochar. The method includes the steps that powder grinding, humidifying, pelleting, low-temperature drying, middle-temperature presintering, high-temperature sintering and cooling are carried out on the sludge pyrolytic biochar to obtain the ceramsite. The device comprises a quantitative feeding device, a water adding device, a humidifying device, a forming and pelleting device, a drying device, a middle-temperature presintering device, a high-temperature sintering device and a cooling device. The sludge pyrolytic biochar is used for preparing the ceramsite, large-scale utilization of the sludge pyrolytic biochar is achieved, heavy metal element in the sludge pyrolytic biochar is further efficiently solidified and passivated, potential heavy metal accumulated pollution of the sludge pyrolytic biochar in the land using process is avoided, and the method and device are particularly suitable for resource utilization of sludge pyrolytic biochar with heavy metal content exceeding standard. The method is simple, practical, low in equipment investment and low in cost and has good economic benefits and environmental benefits.