Differential Optical Absorption Spectroscopy (DOAS) technique is one of the methods used for measurement, analysis and managing air pollution, studying the chemical properties of trace gases in the atmosphere, identification of critical (peak) values to determine the concentration of trace gases that cause an air pollution in industrial-urban locations, and are used in evaluating criteria of photochemical or smog pollution cases of fewer days, and in analysis of wind directions. According to these issues the (DOAS) technique has been developed to become one of techniques that have high order in practical performance based on UV-Visible and near infrared region at spectral range of (200-1100nm) wavelength absorption by molecules of gases in atmosphere. The experimental work of this thesis has been focused on calibration of the system with laboratory experiments to detect many atmospheric gases which are nitrogen oxides (NO, NO2 and NO3 radical). DOAS technique is based on the principle of optical absorption by molecule of gas over several meters to many kilometers length, DOAS gives average concentration measurement lead's to general pollution estimation at long distances, and consequently avoids local perturbation events in point's measurements. The DOAS technique provides typical database by using the language of C # compared with results obtained from experimental measurements.