Abstract. This study included a simple, fast and sensitive method for estimating Amoxicillin (AMOX) in its pure state and in some of its pharmaceutical preparations, this method depends on the modified nanoparticles through oxidation and reduction reactions, With polyvinylpyrrolidone as a stabilizer in a base medium of sodium hydroxide, the (AMOX) drug act as effective reducing agents to dilute the ore mineral salt from silver nitrate (Ag +) to silver nanoparticles, the highest absorption of the oxidation-reduction reaction product of amoxicillin appears at 420 nm. the calibration curve was measured and the following information was calculated and showed compliance with the Beer-Lambert Law within the focus range 0.75-57.5 parts per million. Molar absorptivity was 9.3526 x 10-3 L / mol.cm, and Sandal’s sensitivity was 0.0448 μg/cm2, the standard deviation rate was 0.016%, and the correlation coefficient is 0.9994. The biological effect on some Gram-positive and Gram-negative bacteria was studied and the results were positive in the efficacy of the samples prepared on these bacteria.