The invention provides a flexible sealing film. The flexible sealing film includes a polymer layer and a thermosetting resin layer. The thermosetting layer is arranged on a surface of the polymer layer, and includes: (a) 100 parts by weight of epoxy resin, (b) 50 parts by weight to 100 parts by weight of a phosphorous flame retardant, (c) 20 parts by weight to 50 parts by weight of a toughening agent, (d) 0.1 parts by weight to 2.0 parts by weight of a phosphine compound, (e) 2 parts by weight to 12 parts by weight of silicon dioxide, and (f) 1 part by weight to 10 parts by weight of an ion exchanger. The invention further provides a flexible sealing film and a flexible sealing structure.