Since the beginning of the 21st century，Hong Kong’s economy has been undergoing the third transition. From the perspective of economic development and industrial restructuring，Hong Kong’s service sector is the main theater of the transition. In the transition，Hong Kong’s service sector become more important，its main industries are being upgraded to high value-added segments and its economic function are being transformed to offshore service. With Mainland China accelerating its speed in building a new open economic system，“the Belt and Road” Initiative will provide new opportunities for Hong Kong to strengthen its status as the managerial center of Asian and global value chain，and will be of great help for Hong Kong to succeed in its third economic transition. Therefore，“the Belt and Road” Initiative is in accordance with Hong Kong’s long term economic development strategy，and Hong Kong should actively participate in “the Belt and Road” initiative.