The invention provides a sludge or organic garbage high-low temperature coupling themolysis method which is characterized in that: the method comprises the following steps: step I: the sludge or organic garbage is fed in a low temperature drying depolymerizing furnace; material with partial carbonization is used as raw material of soil organic fertilizer; step II: the material with partial carbonization, generated in pyrolysis, is fed into a middle temperature carbonizing furnace for carrying out carbonization; the obtained bio-organic carbon is used as raw material of soil organic fertilizeror soil conditioner; step III: the material with partial carbonization, bio-organic carbon and one or more than two mixtures of the sludge, straws or organic garbage are fed in a high-temperature pyrolysis furnace for gasification; step IV: fixed carbon remained in a high-temperature depolymerizing furnace after aerogenesis is fed in a high-temperature sub-fusion activated device, and then oxygen-enriched air enters in, and then liquid in a regulating solution storage tank is prayed in for regulation, and then, compound charcoal is obtained after being cooled. The method has high efficiency, simple steps and diversified products.