This research paper investigated the surface characterization and blood compatibility of polyurethane surface modified with Hydrochloric Acid (HCl) treatment for 30 min and 60 min respectively. The surface modified polyurethane with HCl shows increase contact angle and resulted in well-defined structure with unique orientation evident by SEM study. To evaluate the effect of acid treatment on the coagulation cascade, Prothrombin Time (PT) and Activated Partial Thromboplastin Time (APTT) were measured. The HCl treated PU showed increasing Prothrombin Time (PT) and Activated Partial Thrombin Time (APTT) implying improved blood compatibility of the surfaces. The results of Hemolysis assay of the treated surface showed less number of damaged RBC’s compared to control. Compared to control the number of platelet adhesion on the surface of surface modified PU was found less and thereby reduce the chances of activation of blood coagulation cascade suitable for blood contacting biomaterial applications.