The utility model discloses a solid fuel furnace and a step-by-step combined fire grate for the solid fuel furnace. According to the solid fuel furnace, a hearth is arranged in a furnace body; an inclined fire grate is arranged in the hearth; a material push device is arranged on the furnace body at the front end of the fire grate; the fire grate is the step-by-step combined fire grate and comprises a fixed wet-type fire grate part which is arranged in an inclined mode and a reciprocating slag pushing fire grate part which is connected to the lower end of the fixed wet-type fire grate part; and the reciprocating slag pushing fire grate part comprises a fixed fire grate and a slag pushing part which is arranged above the fixed fire grate and can be driven to do reciprocating motion along the upper surface of the fixed fire grate by a driving mechanism. The fire grate of the solid fuel furnace is not easy to damage, the using period of the solid fuel furnace is long, the temperature of the hearth is high, the heat efficiency of fuel can be improved, and the discharge of harmful gas is reduced.