This study is carried to study the types of defects in Plastic Extrusion and Optimization Process Parameters of in UPVC Pipe Manufacturing at Amhara Pipe Factory. The research started by finding the root causes for the occurrence of defects by ‘causes and effect analysis’, frequency of defects by using pareto analysis to improve the quality of product by the optimization of plastic pipe manufacturing process by selecting the most important parameter. The findings of product resistance are also validated by using Hydrostatic pressure Machine experimentally, Taguchi experimental design Method and full factorial analysis. The orthogonal array, main effect of signal-to-noise ratio and the analysis of variance are employed to study the performance characteristics on extrusion process. In this analysis, three factors namely ‘feed speed’, ‘core temperature’ and ‘mixing temperature’ were selected by using PARETO analysis. According to this analysis, burn surface, crack and uneven wall thickness are the priory types of defects. This study is specifically designed for the optimization in the current process. The experiment was analyzed using commercial Minitab17software, interpretation has been made, and optimized factor settings were chosen. So, from the experimental results, core temperature of 165co, feed speed of 16rpm and 110co mixing temperature are the optimal values at which products have high resistance pressure (35.1Mpa)more than the standard pressure (33.8 MPa). The result in both analyses of taguchi experimental design and full factorial analysis has the same response values and also this experiment result is best as compared to the current factory setting parameters at which the products resistance pressure is 24.1MPa. The scrap rate after optimization was reduced from 20%-11.36%