Alginate have gained significant attention in the medical and pharmaceutical industry for their biochemical properties. The purpose of this study was to synthesis of phosphorylated alginate and determinate its impact on the Blood Coagulation Processes. Phosphorylation of alginate was achieved using a Phosphorus trichloride and Phosphorus (V) oxychloride. The degree of phosphorylation and characterization of phosphorylated polysaccharide were investigated by nuclear magnetic resonance spectroscopy (NMR), Fourier-transform infrared spectroscopy (FTIR), inductively coupled plasma – mass spectrometry (ICP-MS), specific surface area (Brunauer–Emmett–Teller method) and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). Influence of phosphorylated alginate on blood coagulation processes were evaluated by the biochemical-hematological tests including evaluation of Activated Partial Thromboplastin Time (aPTT) and Prothrombin Time (PT). The surface modification of alginate sodium salt was successfully carried out by phosphorylation in vapour phase with PCl₃ and POCl₃. The results of biochemical properties showed that the obtained phosphorylated alginates were promising materials to be used in biomedical applications as it was demonstrated they had not significantly impaired blood plasma coagulation.