Physicochemical and rheological characters of agar sample extracted from(rhodophyta)Gelidium sp. collected from the Egyptian coast of the red sea has been investigated. Agar yielded 29% on dry biomass basiswith pretreatment using 0.15 M sodium hydroxide. Agar surface texture was investigated through the usage of the scanning electron microscopy (SEM). Agar is a white flakes and threads, insoluble in cold water, but it swells absorbing much water making hydrogels.The morphology of the agar surface texture was investigated using scanning electron microscopy (SeM).The dynamic rheological measurements of agar solutions (2, 3, 4 mg agar/ml) as a function of shear rate were achieved at 85º C and let to cool gradually (1.5ºC/ min), with the maximum values of  viscosity as following 1.26, 3.12 and 5.18cP, respectively at shear rate of 40 sec^-1.Agr solutions revieled the presence of non-Newtonian fluid material demonstrating shear thinning  (Pseudoplastic) flow behavior in aqueous solution (2 mg agar/ml) giving up to formation of an elastic gel. At higher concentrations (3 & 4 mg agar/ml) induce shear thickening representd as viscosity increases as shear rate increased giving up to Newtonian fluid behavior.The AgNPs were synthesized and characterized on the bases of spectral (FT-IR and UV-visible), morphological (Transmission electron microscopy-TEM), zeta potential and atomic force microscopy (AFM) measurements. The resulted Agar Nanoparticles (AgNPs) are showing gradualproperities as gradual increase in absorbance with increasing the intensity of the yellow-brown color, it showed peak maximum located at 410 nm with absorbance value of 0.579.The average size distributions of AgNPs were found to be   .It was illustrated that zeta potential value for AgNPs was -28.0 mV.