Green chemistry were used for the extracellular synthesis of silver nanoparticles (AgNPs) using algae extracts of Cladophora sp. (macroalgae). AgNPs were synthesized by treating silver ions with a chlorophyll and carotenoid (CC), lipid (L) and boiling (B) extracts of a algae. Reactions were monitored by simple and convenient UV-Vis. Large-scale characterization (size, shape, morphology, charge, elemental analysis and stability) of synthesized AgNPs was investigated by TEM, SEM, DLS and EDS. The results of all these characterization techniques have shown that the synthesized AgNPs by using three different algal ectracts are of different size and stability. However, it has the same optical and morphological properties. The antibacterial activity of the synthesized AgNPs was analyzed by measuring the inhibition zone against gram-negative and gram-positive bacterial strains. As a result, the highest antibacterial property was the CCE-AgNPs with the smallest size and the lowest effect showed the largest size BE-AgNPs. In addition, extracts of Cladophora sp. have different degrees of hydrogen peroxide sweeping capacity and thus show antioxidant activity.