Disclosed is a method for preparing a montelukast sodium salt of Formula 1. The method includes coupling a methanesulfonyl compound of Formula 2 below with a compound of Formula 3 below in the presence of a bistrimethylsilylamide alkali metal salt, further adding an alkali metal base thereto and hydrolyzing the mixture by heating to prepare a compound of Formula 4 below, reacting the compound of Formula 4 with 4-tert-butylcyclohexylamine, followed by purification, to prepare an amine salt of Formula 5, and converting the amine salt of Formula 5 into a sodium salt.