The invention discloses a four-return water curtain smokeless environmentally-friendly boiler which comprises a vertical shell, a boiler furnace and a hearth and is characterized by also comprising an annular air chamber arranged on the inner wall of the hearth, a front smoke box, a rear smoke box, three groups of annular heat transfer smoke tubes and a water curtain dust remover, wherein the front smoke box and the rear smoke box are arranged on the front and rear surfaces of the shell; the rear smoke box is communicated with the hearth, and the front smoke box is communicated with the smoke outlet of the boiler; the three groups of annular heat transfer smoke tubes are used for respectively communicating the rear smoke box and the front smoke box, the front smoke box and a posterosuperior smoke box as well as the posterosuperior smoke box and the smoke outlet of the boiler; and the input port of the water curtain dust remover is communicated with the smoke outlet of the boiler through a smoke exhaust tube, and the output port of the water curtain dust remover is communicated with a draught fan and a dust exhaust chimney through a bent dust exhaust tube. In the boiler, a horizontal boiler multi-return structure is adopted and combined, so that the smoke resistance is increased, and the residence time of smoke in the boiler is prolonged, thus the thermal efficiency of the boiler is improved; and a water curtain dedusting device arranged outside the boiler is used for removing the dust and black smoke in the smoke, thus a smokeless and environmentally-friendly effect is achieved.