Hyaluronic acid is widely used for medical field

tissue engineering and clinical medicine due to its excellent moisture retention

viscoelasticity

lubricity

biocompatibility and biodegradability. The unstability and sensitivity of natural HA to strong acid

base

heat and hyaluronidase limit its clinical application

so the research on modificated HA has been paid more attention. This review concentrates on the recent research achievement on the preparation of HA derivatives by corss-linking

esterification

composition and copolymerization

as well as their clinical application especially in ophthalmic surgery

phonosurgery

osteoarthritis treatment and drug delivery system.