Abstract: Xi’an is the central city of the Guanzhong Plain urban agglomeration and the only national central city in northwest China. It is an important engine for the construction and development of northwest China. The traditional gravitational mode is improved in the parameters such as mass, distance and gravitational coefficient. Based on the revised gravitational model which, the strength of the spatial connection between the central cities of Xi’an and other countries in central and western China and other cities within the city cluster is measured to compare and analyze the gaps and causes of the spatial connectivity between Xi’an and other central cities. The empirical research results show that: (1) Xi’an, the central city in the Guanzhong Plain urban agglomeration, has a relatively low level of spatial connection intensity. The proportion of cities with strong ties with Xi’an in the Guanzhong Plain urban agglomeration is only 30.0% . However, Chengdu and Wuhan have a relatively high proportion of cities with strong ties with other cities in their urban agglomeration, accounting for 60.0% and 48.1%, respectively. (2) Xi’an, the central city within the Guanzhong Plain urban agglomeration and the second-tier cities Xianyang and Baoji, has a low comprehensive development level. Moreover, there is a large gap in the development level between these two levels of cities, making it difficult to effectively exert their radiation and undertaking functions. Compared with central cities in other countries, the overall quality of Xi’an is much lower than that of Chengdu and Wuhan, while the comprehensive quality of the second- tier cities Baoji and Xianyang is 3.4 times lower than that of Xi’an. (3) The comprehensive time distance between cities is an important factor that affects the strength of Xi’an’s spatial connection. Compared with Chengdu and Wuhan, although Xi’an is close to other cities in the Guanzhong Plain urban agglomeration, Xi’an is different from other cities. The city’s comprehensive time distance is still relatively long, which directly weakens Xi’an’s spatial connectivity. Therefore, it is necessary to speed up the construction of the Greater Xi’an metropolitan area and continuously improve the comprehensive strength of the central city. On the other hand, it is also necessary to actively build Baoji City into a sub-central city with stronger comprehensive strength and to perfect Xi’an as the hub of the transportation network system of the Guanzhong Plain urban agglomeration to improve the transportation efficiency between the central city of Xi’an and other cities.

Key words: national central city, Guanzhong Plain City Group, urban spatial connection intensity, modified grav? itational model