The present research on urban external service capability has focused less attention to its spatio-temporal evolution patterns. Aiming to solve this problem, this article comprehensively uses urban flow intensity model, the modified Theil index and K-means cluster as tools to analyze the spatio-temporal evolution patterns of external service capabilities of 286 central cities in Chinese urban system from 2004-2010. The conclusions can be drawn as follows: 1) urban flow intensity value has obvious rise durin...