The invention relates to a preparation method of a flame-retardant dustproof porous polyamide fiber composite material. The preparation method comprises the following steps: adding polyethylene glycol into a polyamide fiber preparation process to form a porous structure; adding porous graphene powder; uniformly stirring; then transferring the mixture to a spinning machine for spinning to obtain polyamide fibers; soaking the polyamide with ethanol, and boiling and filtering; then boiling and filtering the mixture with pure water to obtain the porous polyamide fibers; soaking the porous polyamide fibers in a super-hydrophobic self-cleaning transparent coating for 5-10min and then performing centrifugal filtration for 3-10min to obtain the polyamide fibers, wherein the super-hydrophobic self-cleaning transparent coating is centrifugally separated, and drying the polyamide fibers to obtain the flame-retardant dustproof porous polyamide fiber composite material. The flame-retardant dustproof porous polyamide fiber composite material has the characteristics of good dustproofness, flame retardance and heat isolation and can be used as a multifunctional high-quality clothes fabric.