The breakdown study of Spark gap has long been a research area of interest for many pulse power applications. The electron properties like electron density and temperature are essential for understanding of the discharge properties. These plasma properties can be measured effectively by using a non-invasive approach. Optical emission spectroscopy was employed to study a spark gap with pulse discharges, based on the measurement of certain line ratios. The inter-electrode distance of 10mm was used in the study. Argon, Nitrogen and helium gasses were used as dielectric medium at 0-2 kg/cm2 pressure. An impulse voltage (double exponential pulse with a front time of 1.2μs and tail time of 50μs) is applied to the sparkgap of which electrodes are of rogowsky profile type and thickness of 15mm. The life time of the exited atoms are estimated for argon, nitrogen and Helium gas ambiance for varying pressure conditions. Based on the life time profiles, important plasma parameters such as the electron temperature and electron number density are determined by the intensity ratio of emission lines of excited atoms. It is observed that filling pressure influence strongly the plasma parameters. The obtained results are in agreement over a wide electron density range 109-1015 cm-3. © 2014 IEEE.