The invention discloses a boiler and a using method thereof. The boiler is used, the boiler comprises a water inlet device, a heating device and a waste gas device, wherein the water inlet device comprises a flow dividing box body, a first water inlet pipeline is arranged in the left side end face of the flow dividing box body, and the water inlet pipeline is leftwards connected with the left sidewater outlet of a water pump in a sealed mode; a water inlet at the right side of the water pump is connected with a second water inlet pipeline in a sealed mode; and the second water inlet pipelineis connected with a water source, the first water inlet pipeline rightwards extends to the inner of the flow dividing box body and extends rightwards, moreover, extends upwards to form a first pipeline, extends downwards out of a second pipeline, and the first pipeline extends rightwards to penetrate through the right side end face of the flow dividing box body; and the second pipeline extends rightwards to penetrate through the right side end face of the flow dividing box body, and a flow dividing cavity is formed in the flow dividing box body located between the first pipeline and the secondpipeline.