The present invention relates to a high-temperature heat accumulating type combined boiler arch with built-in rotational flow secondary wind for burning low-grade fuel, which belongs to the boiler technical field, in particular to a high-temperature heat accumulating type combined boiler arch with built-in rotational flow secondary wind for burning high volatile combustible, high moisture, and low heat value low-grade fuel in a highly effective and environment protective burning high volatile combustible, high moisture, and low heat value low-grade fuel boiler. Two high-temperature heat accumulating type cylinder shape rotational flow middle arches are arranged between a face arch and a rear arch, and above the middle and front part of a fire grate, the fore part is connected with the face arch, and the rear part is connected with the rear arch; a round secondary-air air inlet tube is connected with a main secondary air tube, a rotational flow secondary air spray nozzle is connected with the round secondary-air air inlet tube, the round secondary-air air inlet tube is positioned in the high-temperature heat accumulating type cylinder shape rotational flow middle arch, and the outlet of the rotational flow secondary air spray nozzle is connected with the inner wall of the high-temperature heat accumulating type cylinder shape rotational flow middle arch. Because the structure is adopted by the present invention, when the low-grade fuel is burnt, the fuel adaptability is evidently enhanced, the burning working condition in the boiler hearth is stable, the boiler thermal efficiency is improved by about 15 percentage points, and the present invention has the advantages that the fuel adaptability is wide, the thermal efficiency is high, black smoke is not existed, and the effect of the environment protection is good.