Rosuvastatin belongs to a group of medicines known as statins. It regulates the amount of cholesterol and other lipids made by your body, and helps to reduce the risk of heart and blood vessel disease. The dose range 5 to 40 mg orally once daily for a longer period . Presence of higher level of related substances or impurties may have harmful effect on body, hence needed to be identified ,synthesised & charateised for safer use of the medicine. During process optimization of Rosuvastatin calcium(Anti lipidemic drug), impurities ranging from 0.03 to 0.3 % were observed. These related substances or impurities were isolated, characterized and proposed structure was confirmed by chemical synthesis. The structure of these impurities were assigned as Bis 7-(4-fluorophenyl)-6- isopropyl-2-(N-methyl-N-methanesulfonylaminopyrimidin)-5-yl]-3R-hydroxy -5-oxo-(E)-6-heptenoate calcium (5- keto acid), 6-[(E)-2-[4-(4-fluorophenyl)-6-isopropyl-2-(N-methyl-N-methanesulfonylaminopyrimidin)-5-yl] vinyl-4- hydroxytetrahydro-2H-pyran-2-one (Lactone), Bis (+) 7-[4-(4-fluorophenyl)-6-isopropyl-2-(N-methyl-N-methane sulfonylaminopyrimidin)-5-yl] (3R, 5R) - dihydroxy-(E)-6-heptenoate calcium (3R, 5R-isomer), Bis (+) 7-[4-(4- fluorophenyl)-6-isopropyl-2-(N-methyl-N-methane sulfonylaminopyrimidin)-5-yl] (3S, 5R) - dihydroxy-(E)-6- heptenoate calcium (3S, 5R-isomer) respectively. Investigation for the cause of these impurities helped in improvement of yield in bulk preparation of drug. The formation, synthesis and characterization of the Rosuvastatin calcium impurities are discussed.