The invention discloses a high-insulation fiber-adding antiflaming blow-molding nylon composite material and a preparation method thereof, wherein the composite material is prepared from the following components in parts by weight: 50-70 parts of PA66, 10-20 parts of EOVA, 5-10 parts of MXD6, 1-5 parts of compatilizer, 15-20 parts of glass fiber, 20-25 parts of flame retardant, 5-10 parts of plasticizer, 0.1-0.3 part of heat stabilizer, 0.1-1 part of antioxidant and 1-5 parts of nanometer montmorillonite. The high-insulation fiber-adding antiflaming blow-molding nylon composite material is prepared by firstly mixing all raw materials in a high-speed machine, and secondly extruding and pelleting the mixed raw materials by a double-screw extrusion pelletizer within the temperature range of 190-250 DEG C. The invention has the advantages of high insulation, high rigidity, high heat resistance, halogen free, fire resistance, single-layer blow-molding, concise and convenient technology and the like; and in addition, the invention greatly reduces the cost and improves the competitiveness in the market on the premise of guaranteeing quality.