Poly(p-xylylene)(PPX) membranes were prepared by chemical vapor deposition polymerization.Chemical surface modification of PPX membranes by succinic anhydride and maleic anhydride was carried out.Thus the active substituting groups of carboxyl have been successfully introduced into the surface of PPX membranes.The surface roughness of PPX after modification increases a little but still within 10 nm.The water contact angle after the modification decreases obviously.The antioxidation time of PPX-SM-COCH2CH2COOH is the same as PPX of 35 h

while the time of PPX-SM-COCH==CHCOOH decreases 3 h due to the existence of double bond in the membranes.The heparin content of surface modified PPX after heparinization is near 7 μg/cm2. The platelet adsorption test shows that the herinized PPX membranes have good blood compatibility.The improvement of blood compatibility is mainly concerned with the surface heparin content and whether the heparin molecules could maintain the anticruor configuration freely.