The invention relates to a triazine triphenyl phosphinic acid isopropyl ester flame retardant composition and an application method thereof. The flame retardant composition is prepared by compounding and uniformly mixing any two, three or four of melamine cyanurate (MCA), melamine pyrophosphate (MPP), 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and pentaerythritol methyl silicate (PEMS) with triazine triphenyl phosphinic acid isopropyl ester (TTPI) at any proportion, wherein the weight part of the TTPI is greater than zero. The flame retardant composition provided by the invention has the advantages of multielement synergic effect, good flame retardancy, good compatibility with materials, low cost, zero halogen, environmental protection and the like, can be used as a flame retardant for polyester PET, polyester PBT, polyurethane, polypropylene, epoxy resin and other materials, and has excellent application and popularization prospects.