The present invention pertains to the technical field of wastewater treatment, in particular to hydrophilic polyurethane absorbent containing sulfhydryl for removing Hg and a preparation method thereof. The present invention takes water and volatile non-water solvent as the mixed solvent, introduces chloromethyl thiirane monomer as the cross linking agent into hydrophilic polyurethane dispersion dope and finally carries out coating and solidification, thus obtaining the hydrophilic polyurethane absorbent containing sulfhydryl. The present invention has the advantages of simple and convenient technique, high production efficiency, high product quality and low cost. The composition of the prepared absorbent is controllable with the size of 50 to 250mm, the prepared absorbent has the advantages of large specific surface area, strong Hg-ion absorption capacity and rapid absorption rate. In addition, the present invention with excellent high-concentration Hg-ion absorption capacity and trace Hg-ion absorption capacity, good mechanical property and damage ratio lower than 0.5 percent after being used for a plurality of times can be applied to Hg, lead, cadmium and other heavy metal industrial wastewater treatment within a more extensive concentration range.