The invention discloses a flame-retardant textile material and a preparation method thereof. The flame-retardant textile material is prepared from the following components in parts by weight: 60-68 parts of polysulfonamide fiber, 11-15 parts of allyl phenyl isopentene ether, 8-13 parts of chitosan fiber, 4-6 parts of benzoyl butyl acetate peroxide, 2-3 parts of polydecamethylene adipamide, 1-2 parts of trimethyl triphenyl cyclotetrasiloxane, 1-1.8 parts of bis-(phenyl dimethyl siloxane) methyl-silanol, 0.8-1.8 parts of 7-methoxy-8-isopentenylcoumarin, 0.5-1 part of sodium tripolyphosphate, 0.5-1.8 parts of propylparaben, 0.2-0.8 part of trimethylamine acetate, and 0.2-0.6 part of dithio-isooctyl acetate di-n-octyl tin. The invention also provides a preparation method of the flame-retardant textile material.