The invention relates to a photocurable polymer, a coating composition based thereon, a hydrophilic lubricating coating and a product. The photocurable polymer is prepared through copolymerization ofa water-soluble polymerizable photosensitive monomer and a hydrophilic monomer. The water-soluble polymerizable photosensitive monomer comprises: 1) a unit containing a photosensitive structure; 2) aunit containing a quaternary ammonium salt structure; and 3) a unit containing an unsaturated bond structure. The coating composition needs no addition of a small-molecular photoinitiator, so the problems of residues, migration and the like of the small-molecular photoinitiators in a coating can be avoided, and the coating composition has excellent biosafety and compatibility. The coating composition can form the uniform and stable hydrophilic lubricating coating via a simple continuous dip coating-light curing process. When the coating composition coats the surfaces of medical apparatuses andinstruments, the medical apparatuses and instruments have the same smooth touch as loaches after wetting; and after repeated rubbing 30 times in the simulated human tissue environment, the coating does not fall off, is not decreased in lubrication degree, and has excellent firmness.