There is no doubt that the modern scientific studies must keep pace with the era of technology and openness of knowledge has brought about nanotechnology and its applications tremendous leap in various branches of science, especially in the field of industries, including textile contained in the introduction of nano- particles in textile materials during the manufacturing or processing. Silver nitrate has received multiple nanoscale application, especially in the medical and preventive field they are used as a medicine anti- infective and disinfecting agent in wet bandages to help heal wounds and used as acaustic to remove warts and other skin diseases. The research problem lies in the possibility of processing fabric underwear for athletes using nanoscale silver particles to reduce bacteria and prevention of skin diseases that are spread among athletes. Research aims at getting use of nanotechnology to improve the functional performance of athletes underwear, the study used silver nanopraticles to treat 100% woof knitwear with three structures (interlock- Jersey - ripe ) then performing lab tests : wight of square metre – cloth air permeability – cloth water permeability – explosion resistance – bacterial resistance ..... to difine treated cloth characteristics changes, the best structures and the best nano silver nitrate concentration, results revealed that treated studied cloth with silver nanopraticles icreases bacterial resistance which is suitable to protect athletes from skin desies comparing untreated cloth. The empirical research methodology and analytical follow, the results showed a significant effect of the structural composition of the weft knitted fabrics on the permeability of fabrics for water and air permeability and resistance to the blact-resistant bacteria. The lack of a moral about the structure of the fabric of the in crease in we ight after the impact and the rate of drowth of fungus treatment. The results showed asignificant effect of the concentration of silver nitrate nanometer on the increase in weight after treatment and the permeability of fabrics to air waterproof and explosion and the rate of growth of fungus _ resistant bacteria. Research guided to the best structure to improve the functional performance of Athletes underwear is (bell treated with silver nanopraticles with concentration of 30 mic g/ml ) while the worst is (ripe treated with silver nanopraticles with concentration of 30 mic g/ml )