The invention discloses a preparation method and application of special quenching liquid for 50Mn steel, and belongs to the field of heat treatment quenching technologies. The quenching liquid comprises, by mass, 18.1-19.1% of water glass, 1.1-1.3% of NaOH, 25.2-26.3% of sodium chloride and the balance of water, wherein the modulus of the water glass is 2.4, and the baume degree of the water glass is 56. The quenching liquid prepared through the method has the advantages of being uniform in cooling speed, good in quenching performance and dispersity, high in storage stability and not prone to deterioration. A 50Mn steel bearing ring obtained through a quenching method is moderate in hardness, uniform in internal structural form and free of quenching cracks.