Full-automatic modular countercurrent water heater

The utility model discloses a full-automatic modular countercurrent water heater. A heat exchange cavity is formed between an inner shell and an outer shell; a combustion nozzle of the combustor extends into the upper part of the inner shell; a plurality of spaced heat exchange tubes are arranged at the lower part in the inner shell; two ports of each heat exchange tube respectively extend into the heat exchange cavity from the left side and the right side of the inner shell; a smoke outlet is formed in the bottom of the inner shell and located below the heat exchange pipe. A heated medium inlet communicated with the heat exchange cavity is formed in the lower portion of the outer shell, a heated medium outlet communicated with the heat exchange cavity is formed in the upper portion of theouter shell, the gas stove further comprises a controller and a temperature sensor arranged at the heated medium outlet, and the temperature sensor and the combustor are both connected with the controller. The water temperat