Large cities provide powerful and important spatial support for the development of new economy. This chapter made a comparative analysis of the New Economy Index of 20 typical large cities both in China and the United States in 2017. The results show that the average level of new economy of typical cities in China lags behind that of the United States. Chinese cities such as Beijing（ranked 4th），Shenzhen（6th），Shanghai（8th），Hangzhou（9th）and American cities such as San Francisco（1st），New York（2nc），Boston（3rd），Seattle（5th），Los Angeles（7th）and Houston（10th）are in top ten. San Francisco ranks first in 20 cities with a total index of 70.93，and shows advantages in almost all indicators，especially in innovation，digitization and intelligence. New York’s comparative advantages lie in greening，digitization and networking. Boston shows advantages in innovation and greening. From the perspective of indicators comparison，it is found that Beijing shows comparative advantages in innovation capacity and digitization，Seattle in greening and networking and Shenzhen in globalization and intelligence. Los Angeles shows a balanced distribution of all indicators. Shanghai has the highest globalization level while none of other indicators are in the top five，among which the greening is relatively low. Hangzhou and Houston show relatively high score of intelligence. Networking in Washington D.C. and digitization in Chicago are relative high-ranking indicators in two cities respectively. Intelligence and globalization score in Guangzhou is prominent. The reason for its low ranking among 20 cities is that it is influenced by other indicators，especially innovation capacity. The New Economy Index of Wuhan，Tianjin，Chongqing and Xi’an are far behind those of other cities. Finally，some suggestions were made for the development of China new economy from the practices of San Francisco，New York and Boston. Such as fostering innovative and entrepreneurial environment，building “intellectual core” and accelerating the development of higher education and scientific research institutions，promoting the attraction and global connection of innovative factors，enhancing the spatial agglomeration benefits and expanding the space for industrial development，and combining the characteristics of new economic industry and the corresponding resource endowment advantages of the cities.