A polymer for forming an organic anti-reflective coating layer, which is soluble in alkali solutions so that an additional etching process of anti-reflective coating layer is not required, and a composition including the same are disclosed. The polymer for forming an organic anti-reflective coating layer has the following formula. Wherein, R1 is a hydrogen atom (H) or a methyl group (—CH3), R2 is a sulfur atom (S) or an oxygen atom (O), R3 is a group containing 1 to 20 carbon atoms and a terminal hydroxyl group, R4 is an alkylene group or a cycloalkylene group, and if necessary, a hetero atom is contained therein, and a, b and c independently represent weight % of repeating units constituting the polymer, and are 1 to 98 weight %, 1 to 98 weight %, and 1 to 98 weight %, respectively.