Abstract of the Invention Present invention discloses preparation of covalent conjugate Heparin -polymer using carboxyl group of Heparin sodium and terminal hydroxyl and/or group of amino group of polymer. This attachment is conducted for increasing the compatibility of polymer without affecting the properties of polymer and Heparin. For conjugation, the chemical reaction is conducted using catalyst and coupling reagent in presence of solvent. The ACT and TBA method is accomplished to determine total Heparin content of final product. For bio-compatibility, Protein Adsorption, APTT, PT, Platelet Adhesion and Leukocyte Adhesion of conjugate material are investigated. Degradation study of Heparin -PLLA is also carried. Covalently attached Heparin -Polymer is further used in various pharmaceutical industries.