The invention relates to a wetting agent used for pretreated enhancement type filter cloth, which is characterized by comprising the following components by weight ratio: 2-2.5% of color fixing agents, 2-2.5% of epoxy resins, 2.5-3% of water-soluble unsaturated polyester resins, 0.5% of A151, 0.5% of alcohol, 0.2% of tween-80 and the balance water. The pH value of the wetting agent is regulated to5 by glacial acetic acid. The filter cloth weaved by the yarns adopting the wetting agent formula can directly undergo surface chemical treatment without dewaxing, thus saving the electric energy andmaintaining the strength of the filter cloths. The wetting agent overcomes the defect that the existing filter cloth weaved by the yarns adopting the paraffin wetting agent formula need dewaxing before surface chemical treatment, which not only consumes the electric energy but also damages the cloth cover strength.