Protocatechualdehyde (PCA) is one of the effective ingredients extracted from Danshen (Radix Salviae Miltiorrhizae) and was employed to modify the silk fibroin (SF) by graft polymerization and surface adsorption. The surface composition of modified SF was characterized by attenuated total reflectance Fourier-transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and UV spectrophotometer. The anticoagulant activity of modified SF was assessed by in vitro coagulation test and platelet adhesion measurement. The endothelial cell affinity was evaluated by a parallel plate flow chamber. The test results indicated that with the introduction of PCA into SF, the anticoagulant activity has been improved obviously. And the SF surface composition altered by PCA, but did not disturb its beta-sheet conformation. Moreover, the adsorbed PCA on SF surface can enhance the endothelial cell affinity. (C) 2008 Elsevier B.V. All rights reserved.