Cross-border mergers and acquisitions (M&A) can more effectively boost the interactive support of domestic and international circulations by making the enterprises more sufficiently bring self-advantage into fully play and by better making use of domestic and international markets and the two kinds of resources. The success or failure of the cross-border M&A is not only related to the management ability of the enterprises but also affected by the international relations, therefore, the connectivity between the home countries and the host countries is conducive to the success of cross-border M&A of the enterprises. The cross-border M&A of different types of M&A enterprises or the targeted enterprises are possible to have different success rates, and the improving effect of the connectivity on the success rate of the M&A also has heterogeneity. By taking the cross-border M&A events of Chinese enterprises along the Belt and Road during 2009-2019 as samples, based on five connectivity indexes, this paper measures the connectivity level between China and the host countries from such four perspectives as policy communication, facility connection, economy and trade integration, and people’s communication. The empirical analysis shows that the rise of the level of policy communication, facility connection, economy and trade integration, and people’s communication has a positive effect on the success rate of the cross-border M&A of Chinese enterprises, among which the boosting effect of facility connection and economy and trade integration is more significant. The success rate of cross-border M&A along the Belt and Road of China’s state-owned enterprises is lower than that of non-state-owned enterprises. The state-owned identity of the M&A enterprises can weaken the boosting effect of policy communication and people’s communication but can consolidate the boosting effect of facility connection and economy and trade integration on the success rate of the M&A events. The success rate of the M&A of the targeted enterprises which belong to sensitive industries is lower than that of the enterprises which do not belong to sensitive industries. The M&A in the sensitive industries can weaken the boosting effect of policy communication, facility connection, economy and trade integration, and people’s communication on M&A’s success rate, and this weakening effect is more significant on the M&A of state-owned enterprises. In Southeast Asia and West Asia, the influence of the rise of the level of policy communication, facility connection, economy and trade integration, and people’s communication between China and the host countries on the success rate of cross-border M&A of Chinese enterprises has significant heterogeneity. Thus, we should continue to push forward and deepen the “five-connectivity” construction, improve the macro-condition and market environment for foreign economic and trade cooperation of the enterprises, uphold double-win and interactive profitability principle in foreign economic and trade cooperation, use interests community development to boost human destiny community development, further implement the subject position of state-own enterprises, actively shape the real market subject image of state-owned enterprises, emphasize the influence of the connectivity on cross-border M&A, and reasonably select suitable host countries and targeted enterprises.