In this work we describe experiments designed to understand the human platelet adhesion to human umbilical vein endothelial cells (HUVECs) cultured on various kinds of chemically cross-linked anionic hydrogels, which were synthesized by radical polymerization. HUVECs could proliferate to sub-confluent or confluent on poly(acrylic acid) (PAA), poly(2-acrylamido-2-methyl-propane sulfonic acid sodium salt) (PNaAMPS), and poly(sodium p-styrene sulfonate) (PNaSS) gels. The proliferation behavior was not sensitive to the crosslinker concentration of the gels. However, the platelet adhesion on the HUVECs cultured on these gels showed different behavior, as revealed by human platelet adhesion test in static conditions. Only a few platelets adhered on the HUVEC sheets cultured on PNaAMPS gels with 4 and 10 mol% cross-linker concentrations, and completely no platelet adhered on the HUVEC sheets cultured on PNaSS gels with 4 and 10 mol% cross-linker concentrations. On the other hand, a large number of platelets adhered on the HUVECs cultured on PAA gels with 1, 2 mol% cross-linker concentrations and PNaAMPS gel with 2 mol% cross-linker concentration. Furthermore, the study showed that promote of the glycocalyx of HUVECs with transforming growth factor-b 1 (TGF-b 1 ) decreased platelet adhesion, and degrade the glycocalyx with heparinase I increased platelet adhesion. The results suggested that the glycocalyx of cultured HUVECs modulates platelet compatibility, and the amount of glycocalyx secreted by HUVECs dependents on the chemical structure and crosslinker concentration of gel scaffolds. This result should be applied to make the hybrid artificial blood vessel composes of gels and endothelial cells with high platelet compatibility.