The present invention relates to a flame retardant epoxy prepreg composite material and its preparation method and its use, the composite material contains 20 to 70% of epoxy resin matrix and 30-80% of fiber reinforced materials; wherein the epoxy resin matrix comprises the following components by mass part: 100 parts of an F type epoxy resin, 10-50 parts of an E type epoxy resin, 5-40 parts of tetrabromobisphenol A, 5-20 parts of a curing agent, 1-10 parts of a curing accelerator, 5-25 parts of a toughening agent, 1-10 parts of antimonous oxide and 20-80 parts of an organic solvent. According to the invention, F46 type epoxy resin containing a rigid frame structure is taken as a main component, the flame retarding and toughening modification are carried out on the resin matrix by a combination technology, the epoxy composite material with high toughness, high flame retardancy and good overlaying manufacturability can be realized, the flue gas density is obviously decreased when the flame is carried out, and the epoxy prepreg composite material possesses important popularization and application prospects in the fields of large aircraft, ships, high-speed rails and the like.