Water content is a crucial factor influencing the enzyme activity in organic solvent.The techniques of water control were investigated in the esterification of Naproxen catalyzed by lipase from Candida cylindracea in isooctane/octanol system. The results demonstrated that the salt hydrate pair —— Na₂SO₄·10H₂O/Na₂SO₄ had the capability of bufferring water. The sensibility of enzyme to water was decreased by adsorbing the lipase on celite —— an apolar carrier. In addition, Esterification could be improved effectively by adding molecular seive to remove the byproduct-water.