Since the foundation of the People''s Republic of China in 1949, the communistic thinking and system of socializing have restricted the development of the global economic liberty. The reform and opening-up of Mainland China in 1979, however, had created Taiwanese opportunities for Foreign Direct Investment (FDI) in China toward further internationalization. Taiwanese projects and amount of FDI in China had been increasing constantly for many years along with the influence of economy factor and non-economy factors. In the past many scholars probe into their influence factors to host country, investment country or political relation factor separately in respect of Taiwan’s investment in China. Different from previous research, this research aims at a comprehensive discussion on Macroeconomic factor and the political relation factor in respect of Taiwanese attending FDI in Mainland China. With the last ten-year situation of cross-strait trade exchanges, in use of cross-strait overall materials, and through real example analysis, this research probes into influence factors of thrust and pulling force that make Taiwanese investment in China. In order to analyze the profile of Taiwanese investment, this research utilizes relevant research document such as investment motives, investment amount, and selection of position. In addition, through a behavior model, this research examine the main variables which affect Taiwanese investment. This research is expected to examine closely and prove how the overall economic factors and cross-strait political relations influence Taiwanese investment. Most importantly, this research provedes Taiwanese companies reference for investment decision-making on the policy of staying in Taiwan or the selection of host country during nationalization. The conclusion is that, the thrust of the public security inside Taiwan as well as the stability of government administration, and the pulling force of the plentiful and cheaper labor force in China are considered to be the main factors for Taiwanese direct investment amount in Mainland China. From the empirical analysis in this research, following are the recommendations: Government shall focus on eliminating the internal problems of public security, positioning the cross-strait relations, and integrating the bicoastal policies. Furthermore, political parties shall establish democracy and improve the stability of government administration. The above-mentioned factors regard as the prerequisites conditions for Taiwanese companies to leave the root in Taiwan. Meanwhile, provided that there is no cheaper labor force in Taiwan any more, for further globalization it is necessary to create the advantages from horizontal and vertical integrations among the cross-strait industries. It is also important to integrate the resources, to keep the development and high value-added brands in Taiwan, and to improve the mechanism of funding back to Taiwan and the capital market. The factors above are considered to be the necessity conditions for “Leaving the Root in Taiwan”.