Bioactive silver nanoparticles (Ag NPs) have been synthesized by reacting aqueous solution of silver nitrate (AgNO3) with plant extracts which act as reducing and stabilizing agent at ambient temperature. The bio-reduction behaviour of extracts of different parts of plant such as Plumbagozeylanica, Cassia tora, Kalanchoegastonis-bonnieri, Euphorbia milli, Tridaxprocumbens, Nyctanthesarbor-tristis, Psidiumguajava and Lantana camara in the synthesis of silver nanoparticles have been studied. The size and size distribution of prepared NPs have been investigated employing UV-vis absorption spectrophotometer, Dynamic light scattering (DLS) and Transmission electron microscopy (TEM). Dispersion destabilization of NPs is detected by Turbiscan. Different parameters such as stirring effect, reaction time, temperature, silver nitrate concentration and amount of plant extract have been studied to find out the optimum condition for synthesis of Ag NPs. Furthermore, biologically synthesized Ag NPs are tested for their antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis.