The invention discloses a polyamide flame-retardant composition and a preparation method of the polyamide flame-retardant composition. The polyamide flame-retardant composition is prepared from the following raw materials in parts by mass: 40-74 parts of polyamide resins, 10-25 parts of hollow glass fibers, 10-18 parts of flame retardant, 5-7 parts of flame-retardant synergists, and 1-10 parts of other auxiliaries. Compared with the prior art, the polyamide flame-retardant composition is high in flame-retardant performance which reaches UL94 V-0 grade; moreover, the hollow glass fibers are added into a preparation formula, so that the density of materials is reduced while the mechanical performance of the materials can be improved, the dielectric property of the materials is improved, and the polyamide flame-retardant composition is high in heat insulation performance and has soundproof and noise-reduction functions.