Cathepsin k belong to the papain superfamily of lysosomal cystein protease,Human being will develop pycnodysostosis,if losing this gene.Cathepsin k has been implicated in various pathological settings,especially osteoporosis.So cathepsin k may represent important drug targets with more attention.Clinical researches show that the inhibitors of cathepsin k can be used to treat osteoporsis,therefore having wide Potential maketable use.This article review recent progress on the researches of cathepsin k and treatment of osteoporosis disease.