Taiwan¡¦s feed Industry contributes remarkably to the food supply chain in terms of animal protein production. However, after FMD breakout in 1997 and join WTO, feedmill companies with past glories start to erode their advantages in the industry ending up termination of business or struggling the competition. Competitive strategies of¡ucost leadership¡vand ¡udifferentiation¡v proposed by Michael Porter, the strategist, clearly pinpoint out the sustainability in competitive advantages. Those outstanding feedmill companies in different regions that can survive through the tough industry challenges and keep expanding their businesses in a successful manner coincide with these two criteria to compete in the industry. By analyzing the competitive advantage in theory and demonstrations, we also apply these ¡§cost leadership¡¨ and ¡§differentiation¡¨ criteria to the case study Greatwall Group as the suggestive sustainable competitive advantages strategies for the coming challenges in the feed industry. Competitive advantage rigidity could be lessened by meeting the ¡§cost leadership¡¨ criteria by reforming the purchasing model using e-commerce, and ¡§differentiation¡¨ strategy by 1) upgrading the nutrition formulation concept to modeling operation considering the integration advantages; 2) re-allocating the resources in service including research, quality control and vet diagnosis. In the mean times, management restructuring to reinforce the leadership and implementation performance will also be the inevitable requirements. Hopefully through the study of this case, it also sheds lights on other feedmill companies as a learning model.