Provided is a composition preventing tissue adhesion and a method for preparing the same, and, more particularly, a composition preventing tissue adhesion which further contains a drug selectively inhibiting inflammatory response and a method for preparing the composition, in which the composition is produced through a chemical reaction by adding a cross-linking agent to an aqueous solution which contains a block copolymer containing a polyethyleneoxide block having the ability to suppress tissue adhesion, and a polymer with 10,000 to 1,000,000 g/mol of molecular weight which can be mixed with the copolymer; the composition is characterized in that the difference of viscosity, absorbance of visible rays region, and stability between the upper and lower liquid layers are within 10% when centrifuging the composition; and also the method for preparing the composition enhances cross-linking homogenization and viscosity stability through simultaneous spraying and stirring methods without a reaction retardant.