Abstract: Silver nanoparticles were prepared by biological method through reducing silver nitrate by lemon extract used as the reductant and protective reagent in water. The influences of lemon juice dosage,lemon peel alcohol extract usage,the amount of lemon peel water extract,silver nitrate concentration,pH regulators,reaction time and reaction temperature on the particle diameter,morphology and stability of nanosilver were examined,and the characterization of synthesized samples were investigated by UV-Vis spectrum and scanning electron microscope. The optical synthesis conditions for silver nanoparticles were determined,and nanosilver had advantages of good dispersibility,uniform particle size and average diameter of 70 nm. Compared with lemon juice and lemon peel water extract,the alcohol extraction process was the best,which was as follows:1.0 mmol/L silver nitrate,9 mL lemon peel alcohol extract,reaction time 12 min and 1 mol·L^-1 NaOH. The synthesis of nanosilver by biological method was green,safe and environment friendly,which had better practical value.