The invention relates to a method for preparing sludge carbon by mechanically dehydrating coupling drying pyrolysis. The method comprises the following steps: sludge receiving storage, mechanical extrusion dehydration, thermal scattering drying, intermediate temperature pyrolysis carbonization, heavy metal curing, and carbon material cooling package; the high-moisture (80%-90%) wet sludge is prepared into a carbon material through deep mechanical extrusion dehydration, thermal drying, pyrolysis carbonization, and heavy metal curing and like process. The sewage treatment cost can be reduced, and the sewage can be thoroughly reduced, no dioxin is produced in the process, the heavy metal in the sludge is cured, the nitrogen, phosphorous, potassium and like nutrient elements in the sludge areretained, the product sludge carbon can be safely applied to the landscaping nutrient soil or fuel, a new outlet is searched for the resource utilization of the sludge, and important social benefit and environment benefit are provided.