Penelitian ini bertujuan untuk mengetahui aktivitas antibakteri kain poliester yang terdeposit senyawa HDTMS (P-HDTMS) terhadap bakteri Staphylococcus aureus ATCC 25924. Larutan HDTMS dibuat dengan melarutkan senyawa HDTMS dalam etanol 4%. Larutan HDTMS kemudian didepositkan pada sampel kain Poliester. Uji aktivitas antibakteri P-HDTMS dilakukan melalui metode difusi dengan mengukur diameter zona bening di sekitar sampel. Hasil penelitian menunjukkan bahwa senyawa HDTMS telah terdeposit pada kain poliester. Hasil uji zona bening menunjukkan bahwa P-HDTMS memiliki diameter zona bening sebesar 9.25 mm pada waktu inkubasi selama 60 jam. Dengan demikian P-HDTMS mempunyai aktivitas antibakteri dalam menghambat pertumbuhan bakteri Staphylococcus aureus ATCC 25924.This research aims to determine the antibacterial activity of polyesterwhich was deposited by hexadecyltrimethoxysilane (HDTMS) against bacteria Staphylococcus aureus ATCC 25924.The HDTMS solution was made by dissolving the HDTMS compound in 4% ethanol. The HDTMS solution was then deposited on a polyester fabric sample. The antibacterial activity test of P-HDTMS was conducted with diffusion method by measuring the diameter of clear zone around the sample.The results of this researchshowed that HDTMS compound has been deposited on polyester fabrics. The clear zone test results showed that P-HDTMS has diameter of clear zone of 9.25 mm at incubation time of 60 hours. Thus, P-HDTMS has an antibacterial activity against Staphylococcus aureusATCC 25924.