Blood-contacting medical devices play a crucial role in clinical interventions, but their susceptibility to thrombosis and inflammation poses serious risks to treatment outcomes and patient safety. This study presents a novel coating that combines dendritic polyglycerol amine (dPGA), dendritic polyglycerol aldehyde (dPG-CHO), and linear polyglycerol sulfate (lPGS) using a layer-by-layer self-assembly method (LBL) on a polystyrene surface. The immobilization of dendritic polyglycerol enhances surface coverage, enabling the incorporation of a higher density of heparin-mimicking lPGS, while the covalent bonding ensures the coating's long-term stability. Compared to the pristine substrate, the coating significantly reduced platelet adhesion and activation. Notably, its hemocompatibility effects persist even after 30 days. Furthermore, co-incubation experiments with RAW264.7 macrophages confirmed the anti-inflammatory properties of the polyglycerol-based coating. These results demonstrate that this heparin-mimetic coating effectively improves the hemocompatibility of polystyrene and has the potential to be applied to other blood-contacting materials.