In the current thesis, the surface of carbon graphite electrode was modified by electrospray deposition of silver nanoparticles. First of all, silver nanoparticle colloids, with a diameter of about 12 nm, were synthesized by chemical reduction method. Analysis of the UV/Vis spectrum confirms this successful synthesis. In this research, parameters of best electrospray deposition and thus the distance among the needle and the substrate was chosen as 14 mm and then the percentage of added methanol as 80%. The scanning electron microscopy (SEM) micrographs confirm the dep‌osition of silver nanoparticles and the formation of a thin layer on the electrode surface. Also studied electrochemical behavior of this modified electrode in a nitric acid solution are studied for the determination of chromium using cyclic voltammetry (CV), linear sweep voltammetry (LSV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The results show that the presence of silver nanoparticles on the electrode increases the catalytic current of chtomium(VI). Analysis of the amount of the active surface electrode shows the 1.30 fold increase in this surface versus in the unmodified electrode. Electrochemical parameters were optimized for the measurement of chromium(VI). First, a concentration of 0.01M nitric acid was chosen. To increase the sensitivity of the method, a Differential Pulse Voltammetry technique in the potential range of +0.90V to -0.10V, with modulation amplitude of 70 mV and scan rate of 20 mV/s was used. A Preconcentration time of 60 seconds at a 0.00 V potential versus the Ag/AgCl reference electrode, was chosen. The study was performed in the concentration range of 0.01 to 80 mg/L of chromium(VI). Detection limit was 0.063 mg/L. The relative standard deviation (RSD%) for 30 mg/L Cr(VI) was 4.6. Impedance studies show that the charge transfer resistance in the modified electrode decreased, which confirms the catalytic effect of silver nanoparticles deposition on the surface. Interference of some cations in water samples was investigated. At the end, this method was used for the measurement of chromium(VI) in real samples of wastewater. Comparing the results, with those of the standard method for measurement of chromium(VI), by the means of t and F tests, reveals the success of this electrode in the measurement of chromium(VI) in the real samples.