Water immersion tubular heater is composed of multi-branch electric heating elements, flange, guide plate and other parts. The tubular electric heating element has high temperature resistance wire in the metal tube, and the gap is tightly filled with crystal magnesia powder with good insulation and thermal conductivity. The tubular electric heating element is used as the heating body, which has advanced structure, high thermal efficiency, good mechanical strength, corrosion resistance and grinding resistance characteristics. A guide baffle is installed in the cylinder body, which can make the water evenly heated during circulation.