Vacuum hot water boiler with double return-stroke smoke tubes

The utility model discloses a vacuum hot water boiler with double return-stroke smoke tubes. The vacuum hot water boiler comprises a boiler body, wherein a combustion chamber is arranged at the bottom of the boiler body and is connected with a combustor; a heat exchange pipe is arranged at the upper part of the boiler body; a backfire chamber is arranged at one end far from the end connected with the combustor, of the combustion chamber; a front smoke box is arranged on one side on which the combustor is arranged, of the boiler body; a rear smoke box is arranged on one side, opposite to the front smoke box, of the boiler body; the backfire chamber is communicated with the front smoke box through a front smoke tube; and the front smoke box is communicated with the rear smoke box through a rear smoke tube and is arranged in the boiler body. According to the vacuum hot water boiler, as being arranged in the boiler body, the front smoke box also participates in heat exchange with heating medium water, and thus th