The invention discloses a secondary ventilation wall type depth staged low-NOx combustion method and device. Primary air nozzles and secondary air nozzles are longitudinally formed in four corners of a tangentially fired boiler alternately. Meanwhile, secondary air nozzles are formed in the positions, close to the center of a hearth, of the front wall, the rear wall, the left wall and the right wall of a tangentially fired boiler body so that 10-40% of secondary air flow can be sprayed into the hearth from the secondary air nozzles formed in the front wall, the rear wall, the left wall and the right wall of the tangentially fired boiler, and accordingly, depth air staged low-NOx combustion of secondary air in the horizontal direction is achieved, and NOx generation in the initial pulverized coal combustion stage is suppressed. Meanwhile, due to the fact that the secondary air is sprayed into the hearth from the ventilation wall type secondary air nozzles, the entrainment function of the secondary air for pulverized coal airflow can be reduced, and the situation that a water cooled wall is scoured due to the fact that airflow tangent circles are too large is prevented; and a layer of air film with the oxygen-enriched atmosphere and a relatively low temperature is formed nearby the water cooled wall so that overheat, slag-bonding and corrosion of the water cooled wall can be effectively prevented.