SMD series mould sweat dehumidifiers are designed to remove the moisture sweat from condensing on the mould surface. Forming of moisture sweat on the mould surface is due to the use of chilled water for reducing the moulding cycle time, particularly while moulding of the PET preforms. To bring about the moisture sweat on the mould surface is because the mould surface temperature is lower than the dew-point temperature of surrounding air, thus the water vapor comes into being, then causes corrosion of mould and effects quality of moulding parts as well as production efficiencies. This series of machine uses honeycomb rotor to carry out dehumidifying function, which generates a dry airflow with dew-point ranging from +5~-10, and ensures the surrounding air of mould remaining in a low dew-point temperature. It provides constant low dewpoint surrounding air to the mould surface all year round without being influenced by the change of seasons.