The invention discloses a smokeless and dustless coal-fired furnace, which comprises an external furnace body, a grate, a conveying device and a power plant; the external furnace body is internally provided with an inverted-cone internal furnace body the upper end part of which is provided with a plurality of vent holes, and an annular cavity chamber is formed by the internal furnace body and a cylinder column body which is sealed and connected outside the internal furnace body; the grate is erected and arranged at two tops of the cylinder column body and the external furnace body; an outlet of a conveyer pipe in the conveying device is arranged in the external furnace body and matched and connected with a lower end port of the internal furnace body; a slag discharge pipe, which is arranged on the external furnace body and provided with a tight door, and a secondary air hose are both connected and communicated with a main air hose, and the main air hose and the slag discharge pipe both go through the external furnace body and are both communicated with the annular cavity chamber; and the secondary air hose is communicated with space in the external furnace body, and the front lower part of the external furnace body is provided with an upper open slot. When in use, water is added into the lower part of the external furnace body, which is sealed by the water surface, coal is input from the lower end port of the internal furnace body from bottom to top, combustion-supporting air supports the combustion in the internal furnace body and in the upper part of the grate, so as to ensure full combustion of the coal, no smoke or dust, environmental protection and energy saving, and compared with a conventional coal-fired furnace, more than 40 percent of the energy is saved.