The invention discloses a flame-retardant insulating polyester film and a production process thereof. The polyester film is prepared from following raw materials in parts by weight: 80-90 parts of polyester chips, 3.5-6.5 parts of a composite fire retardant, 0.5-2 parts of nano-TiO2 particles and 1-3 parts of a barium-zinc heat stabilizer, and the flame-retardant insulating polyester film is prepared by steps of raw material drying, melt-extruding, piece casting, biaxial stretching, heat setting, cooling and rolling up. In the production process, a composite flame retardant of ZnSnO3 is coatedwith Al(OH)3, so that a dense carbon layer can be effectively produced in a promoting manner during combustion of the materials, not only can prevent oxygen and heat from entering the interior of thefilm, but also prevent flammable gas from escaping to the outside of the film, and can achieve a good flame retardant effect; according to the production process, nano-TiO2 particles are added to theraw materials in the preparation process, and a plurality of interfaces can be generated between the nano-TiO2 particles and polyester and indirectly affect the carrier migration, and the addition ofthe nano-TiO2 particles can affect the concentration of carriers in a composite material medium, so that the charge accumulation in the material can be effectively improved and an insulation effect is achieved.