This thesis is based on the M&A case study of Hon Hai and Sharp. Through investigating the past M&A-related theories and literatures, including types of M&A, the motivations of M&A, the process of M&A, and the integration after M&A, and observing the operating conditions and financial performances of companies in the case in recent years, this thesis studies the motivations of Hon Hai, why were Hon Hai willing to invest Sharp which had huge losses? Then it studies the critical success factors of M&A from the M & A process. Finally, it analyzes the organizational, operating and financial challenges of Hon Hai after M&A, as well as the future directions of integration and strategic planning for offering the references to the cooperation or M&A of Taiwanese and Japanese companies in the future.