Polymerization Reaction Engineering is used to understand how the reaction mechanism, the physical transport processes reactor, configuration and reactor operating conditions that affect the macromolecular architecture as well as the morphological properties of the polymer product. By use of modeling methodology, these mathematical models can be classified into Micro Scale kinetic models, Meso Scale physical, transport and thermodynamic models and Macro Scale dynamic reactor ones. These models are used to achieve goals like production cost reductions and more stringent "Polymer Quality" requirements. The Polymerization process of 1, 3 Butadiene has been modeled by Zeigler-Natta Polymerization (ZNP) reaction mechanism. The efficacy of models has been tested by comparing the predicted results on MW and MWD with those available in the published literature. Mechanistic models for Batch & CSTRs in cascade are developed. These models are represented in the mathematical form and simulated by using Solver in Excel Spreadsheet Software here. The results of simulations performed from developed model in conjunction with the reported experimental data for various catalysts are discussed.