The concept of city primacy degree comes with the primary city, which quantifies the scale and influence of the primary city. As the construction of urban agglomeration is accelerating, the primary city has been given great responsibilities to promote the development of the country and the regions.Because the primacy degrees of population and economy are simple, intuitive and easy to measure, they are commonly used as indicators of city primacy degree. The influencing factors mainly include the following five aspects. First, the population growth rate is the direct factor affecting the city primacy degree. Second, the level of per capita income has a great impact on the primacy degree. Third, there’s a positive correlation between openness and city primacy degree. Fourth, the geographical location of the primary city has an important impact on its primacy degree. Fifth, the political system and policies can influence the primacy degree of the city.Although the increase of city primacy degree has scale effect and agglomeration effect on the development of the city itself, it will also bring negative effects such as "big city disease" if the city’s population primacy degree is improperly promoted. Therefore, we need to adjust the measures to local conditions and make efforts to solve the weak links of the city primacy degree in different regions. For example, Nanjing should make great efforts to improve the primacy degree of innovation.
