The invention discloses a polyamide hot melt adhesive used for clothing a preparation method thereof. With the protection of nitrogen-gas, an unsaturated fatty acid dimers comprising carbon numbers between 12 and 20, an dicarboxylic acid comprising carbon numbers between 6 and 12, a molecular weight regulator, a diamine, a lactam, water and a stabilizer are subject to lower temperature and pressure and dehydration in reactions, next, an N-diethylamine- propyl-Octadecanamide, a nonyl phenol, condensation products of formaldehyde and tetraethylenepentamine are added in and stirred. After the series of reactions, the polyamide hot melt adhesive is obtained. The polyamide hot melt adhesive of the invention of used for clothing has the advantages of narrow molecular weight range, rapid solidification and excellent performance of water resistance and solvent resistance, etc.; the copolyamide is modified by adding appropriate proportions of condensation products of N-diethylamine propyl-Octadecanamide and mnnnich amide, so as to improve the water resistance and solvent resistance substantially. The loss rate of peeling strength of the products obtained is less than 20 percent after alkaline cleaning above 60 DEG C; the loss rate of peeling strength of the products obtained is less than 10 percent after dry cleaning by tetrachloroethylene.