The invention relates to high-strength antiflaming polyester industrial filaments and a preparation method thereof. Particularly, by utilizing processes of low-temperature vacuum viscosity improvement, high-temperature viscosity improvement and high-temperature solid-phase viscosity improvement, phosphorus-containing viscosity-improvement polyester chips are prepared, and by utilizing a melt spinning process of the antiflaming viscosity-improvement polyester chips, high-strength antiflaming polyester industrial filaments are prepared. The intrinsic viscosity of the antiflaming viscosity-improvement polyester chips is 1.05-1.25 dL / g, the terminal carboxyl group content is 12-22 mmol / kg, the average molecular weight is 35,000-45,000, the molecular weight distribution coefficient PDI is 1.05-1.08, the phosphorus content is 0.3-4.0 wt%, and the limit oxygen index is 28-36%; the linear density of the high-strength antiflaming polyester industrial filaments is 200-5,000 D, the single filament fineness is 1.5-20 dpf, the breaking strength is 6.5-7.6 cN / dtex, the content of phosphorus in fibers is 0.3-1.0%, the limit oxygen index is 28-34%, and after a plain weave fabric is washed with 0.1mol / L sodium hydroxide for 15 minutes at 80 DEG C, the limit oxygen index is greater than or equal to 28%. The high-strength antiflaming polyester industrial filaments have high strength, excellent antiflaming performance and good washable performance, are used for the fields of advertising cloth, fire-fighting hoses, oil containing bags of military boxes and the like and have an important application prospect.