The current study uses a hydrothermal technique to demonstrate the antibacterial activity of silver- doped bismuth selenium nanoparticles. Because they are more biocompatible, nanoparticles made of metals, polymers, or lipids are better suited as antibiotics. They behave like molecules, breaking through bacterial cell membranes to obstruct the molecular process. According to the studies, the activity against bacteria is caused by the host immune system being triggered, RNA and protein synthesis being inhibited, biofilm development being inhibited, cell membrane disruption occurring, or reactive oxygen species (ROS) being produced. Low toxicity and a well-established medicinal agent characterize bismuth. It had the property of good X-ray contrast agent due it is huge atomic mass (Z=83). The human body need selenium as a necessary component. In the present work, the prepared Ag doped bismuth selenide nanostructures are characterized using XRD, HRSEM with EDAX. The antibacterial property of Ag doped bismuth selenide nanostructures against gram-positive bacteria S. aureus and gram negative Salmonella enterica analysed by disk diffusion method. The optimized structure, structural parameters, Homo-Lomo, molecular electrostatic potential, dipole moments, polarizability and hyperpolarazibilary are analyzed using DFT method.