Taiwan and Mainland China in 2009 together signed Cross-Strait Anti-Criminal Cooperation and Mutual Legal Assistance agreements that laid a firm foundation for cooperation against cross-strait crime. Although the Ministry of Justice in Taiwan has served as the secretary in the cooperation, there has not been any involvement by its counterpart in Mainland China, which has made cooperation difficult, especially when there are conflicts over sovereignty between the two sides. While Mainland China's one-party authority will not change in the near future, in the ROC if the ruling party does change, it may threaten the very existence of the agreement because the opposition party is more likely to pursue Taiwan's independence. How to maintain the cooperation in the fight against crime across the Taiwan Strait should be a concern of students of the relationship across the Taiwan Strait. This article intends to show that the CCP's Political and Legal Affairs Committee has a most important role to play in guaranteeing mutual legal assistance across the Taiwan Strait.