Three types of stearyl poly (ethylene oxide) (SPEO) with Mn of 2300, 6000 and 12000 were ynthesized; accordingly, three types of amphiphilic coupling-polymer SPEO-MDI-SPEO (MSPEO) were prepared by the reactions with 4,4 -methylene diphenyl diisocyanate (MDI). As the surface-modifying additives (SMA), MSPEOs were coated onto the outer wall of the medical guiding catheters. Due to the lack of tability, when coated, MSPEO blended with the film building agent (FBA), poly(ether urethane) (PEL). The process of coating was performed with a lifter. With invariable speed, the PU guiding catheter was vertically dipped into the coating mixture of SMA-MSPEO and FBA-PEL. The surface analysis was carried out by ATR-FTIR and contact angle measurements. It was proved that the surface enrichment of PEO on water interface was much higher than that on air interface. Three kinds of static clotting time tests, PRT, PT and TT, as well as the static platelet adhesion experiment were performed. The results indicated that the coated surface could resist the blood coagulation electively. In order to test the blood compatibility of the coated catheters under a shear of blood #ow, the dynamicexperiment was performed with a closed-loop tubular system under a shear rate of 1500s. The blood regular testing was carried out on the samples taken out at six di!erent times (0, 5,10, 20, 30 and 60min). The results were ideal. Finally, the SMA-MSPEO was proved to be non-acute-toxic by LD