The invention discloses a high saline alkali reactive brilliant blue KN-RSR dye composition and a preparation method thereof, which belong to the technical field of reactive dyes, and solve the problem that reactive brilliant blue molecules are easily associated and hydrolyzed to separate out in the prior art. The high saline alkali reactive brilliant blue KN-RSR dye composition is a homogeneous mixture based on a complex synergism principle, and utilizes a supramolecular chemistry theory, so that the defect that the saline-alkaline resistance of reactive brilliant blue KN-RSR is poor under the condition of conventional dyeing is improved, meanwhile, the enhancement performance of dye is increased, and the dye composition has excellent leveling property and pile-onproperties; the high saline alkali reactive brilliant blue KN-RSR dye composition not only can be used for dyeing cheese and finished garment which have higher requirements on leveling property, but also can be applied in currently favored energy-saving and environment-protecting dyeing: cold padder dyeing.