As a rapidly-evolving global technology, nanotechnology has presumably brought drastic changes to our lives in the past two decades using engineered nanoparticles, whose penetration into industrial and non-industrial wastewater requires examination of their probable effects in aquatic ecosystems. The main aim of this work is to determine the toxicological and biological effects of nanomaterials. Experiments on exposure of Dunaliella salina to SiO2 nanoparticles were performed for 72 hours with 7 treatments, two controls and three replicates were in each treatment and daily counting of cells was done in each tube. Chlorophyll a and carotenoid were determined through spectrophotometry method after extraction. Imaging of nanoparticles encountering algae cells was performed using cell imaging method by scanning electron microscope (SEM). The population growth rate alterations were evaluated. Probit analysis and softwares such as Excel and SPSS21 were used for data analysis. After exposure to SiO2 NPs, a significant difference was observed between chlorophyll a and carotenoid compared with control (p<0. 05) and also carotenoid content was decreased with increasing the concentration in treatments and a significant difference was observed (P <0. 05). Also, SiO2 NPs caused to inhibit growth in Dunaliella species.