This thesis is focused on the study of the preparation and characterization of zinc oxide nanoparticles in different sizes and shapes and their antibacterial activity. Zinc oxide nanoparticles were prepared in four different methods (a), at a fixed percentage of the molar ratio of zinc nitrate, polyvinylpyrrolidone and different ratio of ascorbic acid, where sodium hydroxide used to calibrate the reaction at pH 7 and temperature was 60℃ (b) at a constant molar ratio of zinc nitrate and different ratios of polyvinylpyrrolidone at pH 7 and temperature 60℃. (c) at a fixed molar ratio of zinc nitrate, polyvinylpyrrolidone, constant high concentrations of ascorbic acid and a pH value changed from 6 -12 at temperature 60℃. (d) Zinc oxide nanoparticle doped by silver was prepared by dissolve a fixed molar ratio of zinc nitrate with variable percentages of silver sulfate in distilled water and using a fixed molar ratio of sodium hydroxide, sodium dodecyl sulfate, absolute ethanol and polyethylene glycol at a temperature of 80℃ for a fixed period of three hours.