Red mud is an industrial waste generated during the production of alumina by Bayer’s process. General purpose polyester resin is used as a matrix and banana fiber as reinforcement. This paper presents a new approach for the optimization of fabrication parameters on red mud filled banana fiber treated and untreated polyester composite with multiple response based on orthogonal array with grey relational analysis in order to save the initial experimental cost on number of specimen and experimental duration. In this study, fabrication parameters namely red mud percentage, fiber treatment, length of fiber, weight fraction of fiber are optimized with consideration of multi response such as impact strength, flexural strength, and tensile strength. A grey relational grade is obtained from the grey analysis. Based on the grey relational grade, optimum level of parameters has been identified and significant parameters are determined by analysis of variance (ANOVA). Experimental result has shown that the responses in the fabrication process can be improved effectively through the new approach.