MSD series mould sweat dehumidifiers are designed to remove moisture sweat from condensing on mold surface. Moisture condensation on the mold surface is due to the use of chilled water for reducing molding cycle time, particularly while molding PET preform. When mold surface temperature is lower than dew-point temperature of surrounding air the water vapor comes into being which leads to moisture condensation, and then affect product quality and production efficiency as well as bring corrosion to the mold surface and cause environmental pollution. This series of machine uses honeycomb rotor to carry out dehumidifying function, which provides constant low dew-point drying air for the molding machine. It greatly reduces the reject ratio by making mold out from moisture condensation.