The invention discloses a staged air supply low-nitrogen gas boiler. The boiler comprise a combustor, a secondary air system, a boiler furnace and a boiler body, wherein the secondary air system comprises a secondary air sleeve, baffle pieces, a secondary air pipe, a secondary fan, an electromagnetic valve and a flowmeter, and the staged air supply low-nitrogen gas boiler is characterized in thatthe combustor is located at the front end of the boiler body, the length of the secondary air sleeve is equal to the length of the air pipe of the combustor, the secondary air sleeve is fixed on the outer side of the air pipe through the baffle pieces, and the baffle pieces are in a spiral line shape; the left end of the secondary air sleeve is sealed and closed, and the lower portion of the secondary air sleeve is connected with the secondary air pipe, and the right end of the secondary air sleeve and the air pipe of the combustor both penetrate through the front panel of the boiler body andare inserted into the boiler furnace; the electromagnetic valve and the flowmeter are installed on the secondary air pipe, and the lower end of the secondary air pipe is connected with the secondary fan below. During operation, secondary air is blown into the secondary air pipe by the secondary fan, and then enters the boiler furnace at a certain angle through the secondary air sleeve and passes through the baffle pieces, and the secondary air and the primary air blown by the combustor are mixed in different areas, staged combustion is formed in the boiler furnace, so that the combustion temperature can be reduced, and the Nox generation amount can be reduced.