Diesel engines are becoming popular because of more fuel efficient and durability. While the CO and HC impurities are significantly lower than in gasoline engines, the design strategies for reduction of Particulate Matter and Nitrogen Oxides remain a major challenge for environment. The work mainly focused on reduction of NOx from diesel engines using SCR technology under Indian driving conditions and furl availability. With BS III/IV fuel available in the country, the catalyst system of choices the Vanadia Tungsten Titania (VWT) system because of its proven resistance to Sulfur poisoning. However, under urban driving conditions on Indian roads, the major obstacle is the low engine out temperatures which are below the normal operating temperature window (200 to 450 °C) of VWT - SCR.The objective of the present investigation is to develop low temperature SCR catalyst system that outperforms the existing commercial catalytic system during the cold start and low load operating conditions. This work focused on modifying the preparation parameters so as optimize the activity of Vanadium for NOx reduction in the temperature range between 200 - 450°C.With the help of sophisticated catalyst characterization tools, novel and highly active formulations of vanadium has been developed, which is more active at lower temperatures as well as do not catalyze the undesirable reactions such as those leading to N2O formation. The metal oxide catalysts are designed and developed to obtain innovative and attractive solutions for the reduction of NOx emissions during cold start and low load operating conditions. The influence of various operating parameters such as NO2/NOx ratio, NH3/NOx ratio, space velocity over the typical temperature range on performance of an optimized SCR formulation are investigated for proper design and sizing of the after treatment system.