The Arbuscular mycorrhizal fungi (AMF) (Funneliformis mosseae), are the most widely distributed symbiont assisting plants to overcome counteractive environmental conditions. In order to improve the sustainability and the activity of AMF, the use of nanotechnology was important. The main objective of this study was to investigate the effect of titanium dioxide nanoparticles (TiO2NPs) on the activity of AMF in common bean roots as well as its activity under salinity stress using morphological and molecular methods. The activity of AMF colonization has increased in the presence of TiO2NPs especially for arbuscule activity (A%), which increased three times with the presence of TiO2NPs. The improvement rate of Funneliformis mosseae on plant growth increased from 180% to 224% of control at the lowest level of salinity and increased from 48% to 130% at higher salinity level, respectively. The AMF dependencies for plant dry biomass increased in the presence of TiO2NPs from 277% in the absence of salinity to 465 and 883% %at low and high salinity levels, respectively. The presence of AMF co-inoculated with TiO2NPs resulted in increasing the salinity tolerance of plants at all levels and reached 110% at salinity level of 100 mM NaCl. Quantitative colonization methods showed that the molecular intensity ratio and the relative density of paired inocula AMF Nest (NS) or chitin synthases gene (Chs) with TiO2NPs were higher significantly P.>0.05 than single inoculants of AMF gene in roots under the presence or the absence of salinity by about two folds and about 40%. Hence, the positive effect of TiO2NPs was confined to its effect on AMF not on bean plants itself.