The invention relates to a seasonal aeration domestic sewage deep denitrification process and device. The device consists of an anaerobic acidification tank, an aeration vertical undercurrent wetland, an aeration-free vertical underflow wetland and a horizontal underflow wetland. Domestic sewage flows into the anaerobic acidification tank; effluent of the anaerobic acidification tank is split and subsequently fed into the aeration vertical undercurrent wetland and the aeration-free vertical underflow wetland respectively; effluent from the aeration vertical undercurrent wetland and effluent from the aeration-free vertical underflow wetland are mixed and subsequently fed into the horizontal underflow wetland. The effluent of the horizontal underflow wetland can be used for replenishing a static landscape water body and the like. Due to arrangement of flow division valves, the aeration vertical undercurrent wetland and the aeration-free vertical underflow wetland, the problem of controlling the ratio of NH4<+>-N to NO3<->N is successfully solved, and the monitoring and management difficulty of the system is alleviated; the device is convenient to maintain, the vertical underflow wetland is aerated continuously when the average weekly temperature is higher than or equal to 15 DEG C, the system TN (Total Nitrogen) removal rate can be greater than 95%, the pollutant removal effect is stable, and the effluent quality can meet the standard of IV-class surface water; the aeration of the vertical underflow wetland is stopped when the average weekly temperature is lower than 15 DEG C, the effluent quality of the system can still meet the one-class B standard of effluent of a sewage plant.