The invention discloses an immersed liquid phase change cooling medium and application thereof in a cooling system of electronic equipment, wherein the cooling medium is a mixture formed by mixing one, two or three of perfluoro-4-methyl-2-pentene, a hexafluoropropylene tripolymer, perfluorohexanone, perfluoroheptane, perfluorooctane, perfluoro-2-methyl-2, 3-epoxy pentane, perfluorohexane and perfluoropentane. The immersed phase change cooling medium provided by the invention has the characteristics of high electrical insulation property, low viscosity, relatively low boiling point, high gasification latent heat, good compatibility and stability, incombustibility, combustion inhibition, low global warming potential (GWP), zero ozone depletion potential (ODP) and the like.