The utility model relates to a fire coal gasification chain grate boiler which comprises a boiler body (1), a gas generating chamber (2), a gas combustion chamber (3), a heat transfer apparatus, a gas supply apparatus, a discharge flue and a fire grate, and further comprises a heat collection chamber (4) which is communicated with a cavity (22) formed by the gas generating chamber (2) and the gas combustion chamber (3) together; and the fire grate is a rotary fire gate (21), an inlet of the fire gate is molded at the cavity (22), an outlet of the fire gate is molded on the heat collection chamber (4), and the distance from the bottom of the cavity (22) to the outlet is larger than the distance from the bottom of the cavity (22) to a fire coal all burnt point at an appropriate transmission speed of the fire grate. By means of the fire coal gasification chain grate stoker boiler, the fire coal can be fully combusted, and the coal cinder waste hate can be fully used.