The invention relates to a dehydration pyrolysis method and system for wet garbage. The method comprises the following steps: 1) squeezing the wet garbage, wherein the temperature condition of the squeezing treatment is 85-101DEG C, and extrusion pressure condition is 5-10 MPa; 2) further increasing the extrusion pressure condition to be more than 10MPa, and completing primary dehydration treatment to provide a solid phase substance obtained by the primary dehydration and a liquid phase substance obtained by the primary dehydration; (3) carrying out pressure relief treatment on a dehydration system subjected to the primary dehydration treatment so as to provide a solid-phase substance obtained by secondary dehydration and exhaust gas, and carrying out condensation treatment on the exhaustgas so as to provide first self-evaporation condensed water; 4) carrying out third dehydration on the solid-phase substance obtained by the second dehydration so as to provide a solid-phase substanceobtained by the third dehydration and a gas-phase substance obtained by the third dehydration; 5) performing condensation treatment on the gas-phase substance obtained by the third dehydration to provide second self-evaporation condensed water, and 6) performing pyrolysis treatment on the solid-phase substance obtained by the third dehydration. The method reduces the moisture of the wet garbage after treatment to less than 50%.