38 cities that has been opened the subway(by the end of 2019)were selected as the research samples to analyze the status quo of the indicators affecting the declaration of subway, such as GDP, urban resident population, general public financial budget revenue and annual average daily passenger intensity. In addition, the correlation between the subway construction index and the above four socio-economic indicators is analyzed respectively from the horizontal and vertical perspectives. The results show that financial resources and subway operation capacity of some cities are still insufficient, so the scale and pace of subway construction should be controlled reasonably. The density of subway in different cities has a strong linear correlation with its GDP and general public financial budget income. However, taking Beijing as an example, the study finds that the subway construction index in the same city at different periods has a high linear correlation with its GDP, urban resident population and general public financial budget income, and the established multiple linear regression model conforms to this law with a fitting degree of over 99%. The research will provide some reference for each city that should reasonably control the subway construction progress according to their own social and economic level, and promoting the orderly development of urban rail transit.