Vascular graft surface properties significantly affect adhesion, growth and function of endothelial cells (ECs).  Biopolymers, gelatin and chitosan, have emerged as highly versatile biomimetic coatings for applications in tissue engineering owing to their excellent biocompatibility and biodegradability.  Chitosan is a polysaccharide, with structure and characteristics resembling those of glycosaminoglycans (GAGs).  Gelatin is a partially denatured derivative of collagen, an important extracellular matrix (ECM) component in natural vascular tissues.  Both chitosan and gelatin have been proven to have good compatibility with vascular cells. N-succinyl-chitosan (NSCS) is a novel biocompatible amphiphilic derivative of chitosan with double bonds, which allow it to be immobilized on polymer surface under UV irradiation.  In this study, gelatin was firstly incorporated into NSCS via chain entanglements. The so formed NSCS/gelatin complex was then polymerized on the surface of polylactide (PLA), with the aim of improving the compatibility of the synthesized PLA with ECs.  X-ray photoelectron spectroscopy (XPS) characterization and water contact angle confirmed that the PLA surface was successfully immobilized with the NSCS/gelatin complex, which in turn enhanced its hydrophilicity.  We also examined the influence of modified surfaces on EC  adhesion, proliferation, function, as well as its antithrombogenicity.  The ECs on the surface-modified PLA films exhibited greater spreading and flattening than that on unmodified PLA films.  The cells on modified PLA surfaces also expressed more and structured intercellular molecule CD31, and uptook more acetylated low-density lipoprotein (LDL) than those on un-modified PLA surfaces.  In addition, 4 times higher cells were retained on the modified PLA surface upon perfusion at a physiological shear stress of 5 dyn/cm² over 24 hours, and the endothelialized surface on the modified surface has a better blood compatibility than that on the unmodified PLA.  These results indicated that modifying biomaterials with the biomimetic NSCS/gelatin complex is an important method that can be used to engineer material surfaces to enhance endothelium function for vascular tissue engineering.