Technological progress is the basic motive force of the development of productivity. The acquisition of technology can be achieved through technology introduction and technology innovation. There are different opinions on whether introducing foreign capital is conducive to the improvement of technological progress of domestic enterprises. But few directly focus on whether introducing foreign capital can introduce core technology.　　Based on the real case of Shenzhen Huakong Seg Co., Ltd. introducing foreign capital, this paper explores the determinants of introducing foreign capital into core technology, and explores the underlying causes from the perspective of motivation of foreign shareholders and local government behavior. According to this case, our conclusions are: (1) Realizing the comparative advantage of technology is the real motivation of the technology transfer of foreign capital, while core technology is the fundamental source of the comparative advantage of technology, and foreign capital often transfers the outdated technology rather than the core technology. (2) Local governments’ overuse of preferential measures provides opportunities for foreign investment to export backward technology and retain core technology while gaining technological control benefits. (3) The introduction of foreign capital does not necessarily bring about technological upgrading effects to the enterprises that attract foreign investment.　　Contributions of this paper are as follows: Firstly, it focuses on core technology when studying on the technical effect of foreign capital, which supplements to the existing literature. Secondly, it combines the characteristics of the times to " attract technology”, which will help us understand the deep logic behind the mode transformation from technology introduction to technological innovation advocated at present. Thirdly, it describes in detail the whole process of the technology transfer of foreign capital and the specific types of technology transferred through a real case, which helps to overcome the limitations of the existing archival studies that are difficult to distinguish the quality of technology. Fourthly, it demonstrates that core technology is the fundamental source for foreign capital to obtain comparative advantage benefits, which provides a realistic basis for the current high-level state to emphasize that core technology cannot depend on foreign capital. This paper also reveals the mechanism that alienation of local governments’ motivation for attracting foreign capital may expand the space for foreign capital to obtain the comparative advantage of technology, which is beneficial to further deepening the policy of opening up to the world and improving the behavior of local governments in attracting investment.