SCR being an advanced active emission technology system for diesel engine, is one of the most cost-effective and fuel-efficient technologies available for complying with the stringent NOx emission legislations. SCR catalyst volume is being considered as the most concerned part for NOx reduction and durability and a key element leading to high financial assessments. The SCR Optimization reduces the possibility of ammonia slip and leads to high NOx conversion rates. By improving the performance of the SCR, the optimization solution also reduces the amount of catalyst needed, thereby reducing associated costs. The decrease in SCR catalyst volume by 1m3 with respect to current set-up will lead to 15% reduction in the total cost of catalyst. All the factors affecting the SCR catalyst volume were focused in detail and the plausible range of catalyst volume was investigated by comparative measurement of these factors. The durability evaluation was done in addition on test bed, it was found that the volume was decreased by 20% and it was further concluded that the application of this study increases the degree of freedom in selecting the catalyst and optimization of catalyst volume but detoriating the NOx conversion. The various iterations performed for the optimization of catalyst have been discussed in this paper with test results to show the comparison study with all.