Objective:To assess the effect of bioactive coatings on biocompatibility of flat Nitinol slices designed for the closure of congenital heart defects in vitro. Methods:①The experiment was divided into six groups: control group, uncoating group, chitosan group(Chi group), chitosan/r-hirudin(Chi/r-Hir) low-dose group, Chi/r-Hir middle-dose group and Chi/r-Hir high-dose group. ②The hemocompatibility of biomaterials was evaluated in vitro in a dynamic model with whole human blood by the hemolysis test and anticoagulant activity such as partial thrombin time(APTT), prothrombin time(PT) and thrombin time(TT) were measured as well. Surface characterizations such as protein adsorption, platelet adhesion and aggregation were observed by scanning electron microscopy. ③Humanumbilical vein endothelial cells(HUVECs) were cultured in the presence of tested slices for 72 h. Adhesion and proliferation of HUVECs were evaluated with light microscopy and fluorescence microscope by double-staining of fibronectin(Fn) and Ki67. Results:①The hemolysis rates of biomaterials were less than 1.7%. ②White blood count(WBC), red blood count(RBC) and platelet count (PC) were normal and no difference was observered between each groups. ③Chi/r-Hir significantly prolong the APTT and TT than those of other groups(P < 0.001). the protein adsorption, platelet adhesion and aggregation were reduced by Chi/r-Hir coated. furthermore, there was dose-effect relationship of differential concentration Chi/r-Hir coated(Dunnetts, P < 0.05). ④After 72 h of incubation, without abnormal morphology, HUVECs were able to grow on to all kinds of slices. The adhesion of the cells on the slices by fluorescence microscopy through the application of Fn immunofluorescent antibody labeled HUMECs decreased as following:Chi>Uncoating>Chi/r-Hir coating. The proliferation of the cells on the slices by fluorescence microscopy through the application of Ki67 immunofluorescent antibody labeled HUMECs decreased as following:Chi=uncoating>Chi/r-hir coating. The cells grown on the surfaces of Chi/r-Hir were not as good as on the Nitinols slices. Conclusion:In vitro, Chi/r-Hir coated with nitinol slices present good anti-coagulation, but adhesion and proliferation of HUVEC is not beneficial.