Abstract: The purpose of this study was attempted to clarify the effects of burnt rabbit sera on the function and structure of endothelial cells in vitro. Manifold methods such as morphological study （inverted microscopy, scanning electron microscopy）, measurements of LDH, 6 keto PGF 1α and tPA in medium, detection of the ability of antiadhesion of platelets to endothelial cells, etc. were used. The main results and conclusions were as follows: （1）There were obvious toxic effects of burnt rabbit sera on endothelial cells accompanied by dysfunction prior to structure injury in which the alteration of endothelial cell surface and intracellular junction appeared earlier; （2）After incubation with burnt rabbit sera, the ability of antiadhesion of platelet to endothelial cell surface which was considered to be one of the primary cause of formation of local micro thrombosis in vivo was reduced. Meanwhile, because of the destruction of endothelial cell surface on which there were a lot of receptors such as tPA, uPA, PAI 1, heparin,etc., the ability of fibrinolysis of endothelial cells also decreased.