The invention belongs to the technical field of automobile chassis armors, and provides a preparation method of a water-based flame-retardant anticorrosion chassis armor. The water-based flame-retardant anticorrosion chassis armor is prepared through high-speed dispersion with water-based nanometer high-molecular polymer as the film forming substance, high-dispersity talcum powder and coarse whiting as the filler, hollow glass beads as the thermal insulation functional filler, zinc phosphate as the anticorrosion auxiliary filler and water-based black paste as the coloring dye. The prepared water-based flame-retardant anticorrosion chassis armor belongs to the improvement and innovation of an existing water-based chassis armor; by adding various nanometer materials, the flame retardance and anticorrosion performance of the water-based chassis armor are greatly improved.