The Microwave System and method of reactivation is designed to provide an indirect, safe and energy efficient source of heat and temperature rise required in the reactivation section of the desiccant unit for the release into atmosphere of the water vapors which are accumulated in the desiccant rotor. This microwave reactivation system and method is based on heat transfer produced from a heated fluid which is pumped through a closed loop coil assembly. This closed loop coil assembly is located and runs through both the isolated heating chamber of the microwave section and the reactivation/regeneration section in the dehumidification system. The airstream passing through the reactivation intake section comes in contact with the coil assembly and is heated to the desired temperature prior to reaching the desiccant rotor.