The invention discloses a molecular sieve regeneration gas heating waterproof method. An air outlet of a heater is connected to a steam discharge pipeline, and provided with a first switching valve; an inlet end pipeline of a first regulating valve is divided into two paths, and the other path is communicated with a regeneration gas inlet pipeline connected to the air outlet of the heater, and is provided with a second regulating valve; a first molecular sieve adsorber or a second molecular sieve adsorber pressurize in sequential control, the switching valves on the two branches of the regeneration gas inlet pipeline are turned off back in place, the second regulating valve and the first switching valve are open, and the regeneration gas is purged back to the heater by the second regulating valve and passes through the first switching valve and the steam discharge pipeline; and the first molecular sieve adsorber or second molecular sieve adsorber depressurize in sequential control, the switching valves on the two branches of the regeneration gas inlet pipeline are turned off back in place, the second regulating valve resumes to a sequential control mode, and the first switching valve is closed. The method is capable of reducing the moisture content of the regeneration gas and prolonging the service life of molecular sieve, and is applicable to a medium-pressure steam regeneration heating system.